Some of the Secret Service agents under investigation in the Colombian prostitution scandal have agreed to take polygraph tests, a U.S. official told NBC News on Wednesday.

Eleven Secret Service agents were recalled from Colombia last week and have been stripped of their security clearances after reports emerged alleging that some of them had taken prostitutes to their hotel rooms before President Barack Obama arrived for the Latin American summit.

The U.S. official said the agents had been "offered" the opportunity to submit to polygraph tests and that some had accepted. The official didn't say how many had agreed.

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Ed Donovan, a spokesman for the Secret Service, wouldn't confirm the information, saying only that the agency's Office of Professional Responsibility was using every investigative tool at its disposal.

NBC News: Prostitute's $50 fee for two agents triggered Secret Service scandal

Secret Service Director Mark Sullivan has told lawmakers that the 11 agents and 10 U.S. military personnel also implicated in the scandal are giving investigators conflicting stories, making it difficult to pin down the truth, several lawmakers told NBC News.

The Colombian government is separately investigating whether underage girls were part of the arrangements, but Sen. Charles Grassley of Iowa, the top Republican on the Judiciary Committee, told NBC News that Sullivan believes the youngest woman involved was about 20 or 21 years old.

NBC News reported this week that some of the agents had copies of the president's schedule in their rooms, raising the possibility of a security breach. But Sullivan said none of the prostitutes ever had access to secure information, according to Grassley.

"I think that he feels that protocol was followed," Grassley told NBC News.

Grassley said Judiciary Committee staff members would meet with agency representatives later this week for a more complete briefing. He said the committee would conduct its own investigation only if members concluded that the Secret Service inquiry "was not doing the job."

Regardless, Grassley said, "I think you'll find their heads are going to roll." He added that he was worried that there could be a culture of misbehavior at the Secret Service, a concern that was echoed by Sen. Susan Collins, R-Maine, who has also been briefed on the case.

Collins told NBC News that her "instinct" is that this wasn't an isolated incident. She said that she pressed Sullivan and that he had told her the agency was "scrubbing the files" for possible previous incidents.

The Defense Department is separately investigating the 10 military members who have been implicated. Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said Tuesday that "we let the boss down" in Colombia.

Defense Secretary Leon Panetta is expected to brief leaders of the Senate Armed Services Committee in the next couple of days, Sen. John McCain, R-Ariz., told NBC News on Wednesday.

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The Colombian prostitute who triggered the scandal that has rocked the Secret Service got angry with two agents who refused to pay her full price for servicing the two of them, leading to a financial dispute over between $40 and $60, according to a government source who has been briefed on the investigation.

Two agents from the service's elite Counter Assault Team, in Cartagena, Colombia, in advance of President Barack Obama's arrival for the Summit of the Americas over the weekend, had procured the women's services at a local strip club called the Pley Club on the evening of April 11. All the Secret Service agents and officers implicated in the scandal are believed to have gone to the club that evening and brought back women, a U.S. official told NBC News.

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The controversy arose after one of the women went back to a hotel room with two agents. The woman wanted to be paid for serving both agents, the source who has been briefed on the probe told NBC News. Instead, the agents would only agree to split her price, prompting the woman to complain to local police who were stationed in the lobby of the Hotel Caribe, the source said.

The police then went up to the agents' room and began banging on the door, which the agents at first refused to open, the source said. There are conflicting reports over how the payment dispute was resolved. But two government sources told NBC News the police contacted the U.S. Embassy over the dispute and Embassy officials then arrived at the scene.

All those with booked rooms at the hotel had to pay a fee of $25 for bringing any guests to their  rooms -- and the guests were required to leave some form of identification at the front desk. A quick scan of the hotel register by a U.S. Embassy official established that 11 Secret Service agents had brought back women to their rooms that evening. When Embassy officials notified Secret Service Director Mark Sullivan, he immediately ordered all the agents to fly home, the sources said.

The Secret Service members -- including agents and uniformed officers -- were stripped of their security clearances on Monday.

Included in that group were two high-level Secret Service supervisors, three counter assault officers whose job is to repel attacks and three sniper-team members, who take to rooftops to secure areas where the president might visit, NBC News reported.

U.S. officials have described the agents' conduct as a potential security breach especially because all the agents involved had access to the president's day-by-day, minute-by-minute schedule. But one official familiar with the security arrangements said that there were no specific security threats during the president's trip. Although agents upon arrival were briefed about current activities by leftist FARC guerrillas and local drug cartels, they were told neither had made any specific threats to the president.

The only specific security concern mentioned was that agents and officers were told to bar a left-wing journalist from events at the summit and were given a flier with the journalist's photograph to keep him out, the law enforcement source said.

The Secret Service sent agents to Colombia to interview the prostitutes who hooked up with the Americans to figure out if the women are under age, involved with terrorism or trafficking in illegal drugs, a lawmaker told NBC News' Luke Russert on Tuesday.

 “They have all their IDs and are conducting an extensive background check to make sure they aren't affiliated with any narcotrafficking or terrorist group or that they could be minors,” Homeland Security chairman Rep. Peter King told Russert. “So far there is no security breach."

King, who was briefed on the Colombia investigation by Sullivan, confirmed that there were 11 agents and 11 women.

"The investigation could take a while simply because of the amount of women involved,” King said. “Some are saying they were prostitutes and others say they weren't."

U.S. military officials told NBC News on Tuesday that 10 American servicemen also were under investigation. According to the officials that includes five Army soldiers, two Navy sailors, two Marines and one Air Force airman.

One military official says it appears that at least two of the service members were found with prostitutes in their hotel rooms, the same Hotel Caribe where the Secret Service detail stayed.

It's not clear whether any of the military members were in any way connected to the allegations involving members of the Secret Service at a Cartagena strip club.

It's also not yet clear whether any of the 10 will face criminal charges.

House and Senate lawmakers are also looking into the allegations. King told The Associated Press that his committee is devoting four investigators to the probe.

Meanwhile, one former Secret Service agent, Dan Bongino who is a Republican candidate for Congress in Maryland, told NBC News that in his 12 years at the agency he never saw anything like what is alleged to have taken place in Colombia.

“I’m not saying it’s never happened, but I never saw it.” Bongino said. He denied there was a culture of partying inside the agency.

Top US military officer: 'We let the boss down' over prostitute scandal

A decade ago, however, U.S. News and World Report published an investigative report detailing criminal activity and extreme partying as well as oversight problems. In one reported incident, members of Vice President Dick Cheney’s security detail got into a brawl outside a bar on a trip to the San Diego area.

As the agency sought to rebuild its image, other high-profile incidents with presidential protection brought more scrutiny.

In 2008, an Iraqi journalist threw shoes at President George W. Bush during a Baghdad visit.

And in November 2009 three people crashed a White House state dinner for Indian Prime Minister Manmohan Singh. Michaele and Tareq Salahi and Carlos Allen were able to get past Secret Security agents at the door and enter the party.

The Salahis even met Obama and had their picture taken with Vice President Joe Biden. In a January 2010 congressional hearing on the matter, the Salahis, who have since divorced, refused to testify, invoking their Fifth Amendment right against self-incrimination.

The prostitution scandal, however, has brought far more intense focus on the Secret Service and behavior by its agents and officers.

"This really is the biggest scandal in the history of the Secret Service," Ron Kessler, author of "In the President's Secret Service," told NBC News earlier this week. He said the agency's problems are deeply rooted.

"There's a culture in the Secret Service that's fostered by the management of just nodding, winking, favoritism," he said. "What the agency needs is an outside director who can come in, clean house, change the standards." 

Michael Isikoff is NBC News' national investigative correspondent; Jim Miklaszewski is NBC News' chief Pentagon correspondent. NBC News Correspondent Luke Russert and msnbc.com reporter Jeff Black also contributed to this report.

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Updated at 11 p.m. ET: A dozen Secret Service personnel providing security for President Barack Obama at an international summit in Cartagena, Colombia, have been relieved of duty because of allegations of misconduct.

The Associated Press said it received an anonymous tip that the misconduct involved prostitutes in Cartagena, site of the Summit of the Americas. A Secret Service spokesman did not dispute the allegation.

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The Washington Post reported that Jon Adler, president of the Federal Law Enforcement Officers Association, told the newspaper the accusations relate to at least one officer having involvement with prostitutes in Cartagena.

A U.S. official, who was not authorized to speak publicly on the matter and requested anonymity, put the number of personnel at 12, the AP reported.

Leftists protest Obama visit with bombs?

Adler told the Post that the entire unit was recalled for the investigation. He later told the AP he had no specific knowledge of any wrongdoing.

The incident threatened to overshadow Obama's economic and trade agenda at the summit and embarrass the U.S. The White House had no comment.

Secret Service spokesman Ed Donovan would not confirm that prostitution was involved, saying only that there had been "allegations of misconduct" made against Secret Service personnel in the Colombian port city hosting Obama and more than 30 world leaders.

“The Secret Service takes all allegations of misconduct seriously,” Donovan told the Post.

Colombia president to Obama: Don't ignore your neighbors

Donovan said the allegations of misconduct were related to activity before the president's arrival on Friday night.

Obama was attending a leaders' dinner Friday night at Cartagena's historic Spanish fortress.

The personnel involved had been sent back to their permanent place of duty and were being replaced by other agency officers, Donovan said. The matter was turned over to the agency's Office of Professional Responsibility, which handles the agency's internal affairs.

"These personnel changes will not affect the comprehensive security plan that has been prepared in advance of the president's trip," Donovan said.

This article includes reporting by The Associated Press.

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Updated at 4:20 a.m. ET: LILLE, France -- Former IMF chief Dominique Strauss-Kahn was handed preliminary charges Monday alleging he was involved in a hotel prostitution ring in France, a stunning blow for the onetime French presidential hopeful.

The investigation on suspicion of complicity in a pimping operation is the latest judicial headache for the Socialist ex-finance minister. The move could lead to a trial but it falls short of charging him.

His lawyer said the married, 62-year-old Strauss-Kahn engaged in "libertine" acts but did nothing legally wrong.

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Strauss-Kahn himself left in a black sedan without speaking publicly. He was released under judicial supervision and was barred from contacting others charged in the case, a judicial official said. The official spoke on condition of anonymity because the investigation is still underway.

The Lille prosecutor's office said in a statement he was required to post 100,000 euros ($133,300) in bail. He is forbidden to contact witnesses, the press and others involved in the prostitution case, it said.

Under the spotlight
Strauss-Kahn has seen his sexual behavior scrutinized in the international spotlight over the past year. The French preliminary charges come two days before a New York court takes up a civil case in which a hotel maid accuses Strauss-Kahn of sexually assaulting her.

The Lille case centers on allegations that a prostitution ring organized by Strauss-Kahn's business associates supplied clients at the city's Carlton Hotel.

Already in the case, eight people, including two Lille businessmen and a police commissioner, have been arrested, and construction firm Eiffage fired an executive suspected of using company funds to hire sex workers.

Strauss-Kahn investigated in French prostitution ring

Judges had the option of putting him under investigation for having potentially benefited from misappropriated company funds if he knowingly attended prostitute sessions paid for by his executive friends using expense accounts.

Instead, the case against Strauss-Kahn hinges on whether he knew he was partying with prostitutes, and whose money was used to pay them. Lawyers for the ex-IMF chief have acknowledged that he attended orgies.

In itself, using prostitutes is not illegal in France.

Prostitutes questioned in the case said they had sex with Strauss-Kahn during 2010 and 2011 at a luxury hotel in Paris, a restaurant in the French capital and also in Washington, D.C., where he lived while working for the Washington-based IMF, judicial officials say.

"Mr. Strauss-Kahn is finding himself, in large part because of his fame, thrown to the butchers," lawyer Richard Malka said. "Colossal police and judicial means were deployed to crack and dissect his private life to an infinite degree, with the only goal being to invent and then castigate what can be considered a crime of lust."

He said it was inappropriate to use "simple libertine activity" to accuse Strauss-Kahn of procuring prostitutes or involvement in organized crime.

French newspapers have dubbed the prostitution investigation "The Carlton Affair" after the name of the expensive Lille hotel where some encounters allegedly took place.

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Strauss-Kahn's wife of two decades, renowned TV journalist Anne Sinclair, is now editor of the new French version of the Huffington Post website. The site carried a banner headline Monday night reading "PRELIMINARY CHARGES" over a photo of Strauss-Kahn.

The Malka suggested that the charges were politically tinged, since they came down a month before France's presidential election. Just a year ago, Strauss-Kahn, a prominent economist, had topped polls as the man most likely to win.

Strauss-Kahn quit the IMF after the New York hotel maid said he sexually assaulted her in May. The criminal charges were later dropped when prosecutors said the maid's testimony was unreliable. Strauss-Kahn said the encounter was "inappropriate" but insisted it wasn't violent.

The maid, an immigrant from Guinea, has insisted she was truthful about the encounter and is pursuing claims against Strauss-Kahn in a civil lawsuit. A hearing is set for Wednesday on Strauss-Kahn's claim that diplomatic immunity should insulate him from the lawsuit. Strauss-Kahn is not expected to attend.

The Associated Press and Reuters contributed to this report.

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The top court in Canada's Ontario province on Monday legalized brothels in an attempt to make prostitution less dangerous for those employed as sex workers.

The landmark decision noted that prostitution is very dangerous and existing laws prevented sex workers from banding together and hiring security guards.

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The case will most likely be appealed to Canada's Supreme Court and a final decision is thought to be at least a year away, according to the Globe and Mail.

Starting in 2013, sex workers will be able to work together in a brothel in any part of the province, the newspaper reported. On April 25, prostitutes will be able to hire body guards, the court decided.

Communicating for the purposes of prostitution will still be illegal, according to the judgement, the newspaper reported. Keeping this part of the current law in place will likely help assuage fears that the new laws will encourage sex workers into overtly propositioning clients in public, the newspaper added.

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A year after the Chinese government started targeting human trafficking, the country’s security ministry reported that in the last year police had rescued 24,000 women and children who had been abducted, the Irish Times reported.

Some women had been sent as far as Angola, in Africa, to be prostituted, the BBC reported. One third of those rescued were children; the rest were women. Most were found during police raids of more than 3,000 gangs dedicated to human trafficking.    

The black market for children is a growing problem in China, the BBC reported, and critics blame the country’s one-child policy. The preference for boys over girls has led to an increase in the trafficking of young boys, many of whom are sold to couples without children, the Irish Times reported.

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Women were bought for labor and as brides for unmarried sons, the BBC reported.

The Ministry of Public Security, as the Chinese police agency is formally called, said it has started using a DNA database of missing children to make it easier to reunite them with their families.

Officials did not say how many people were kidnapped in China in 2011.

Abductions erupted into a nationwide scandal in 2007 after it was revealed that thousands of people were forced into slavery at brick factories and mines, the Irish Times reported. Nearly 600 people were immediately released, many of them teenagers, and one man was sentenced to death, the BBC reported.

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PARIS -- Former IMF chief Dominique Strauss-Kahn has been released from a French police station after nearly two days of questioning over a suspected hotel prostitution ring.

Judicial officials say Strauss-Kahn, a one-time French presidential hopeful whose political aspirations were derailed by a May 2001 sexual assault accusation in New York City, will be summoned again next month by three judges who will decide if there is enough evidence to file charges in a case centering on the alleged prostitution ring in France and Belgium.

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He was held by police for 32 hours and spent the night in a cell, according to NBC News.

Strauss-Kahn held in French prostitution ring

French TV footage showed police restraining reporters behind metal barriers as a tinted-window sedan carrying Strauss-Kahn left the police station in northern city of Lille.

The investigation is focused on a prostitution ring that allegedly supplied clients of Lille's luxury Carlton Hotel. Police want to establish whether Strauss-Kahn knew that women at parties he attended in Paris and Washington were prostitutes.

Strauss-Kahn believed he was participating in swingers' parties and had no reason to suspect that the women were prostitutes, his lawyer Henri Leclerc has said previously. Consorting with prostitutes is legal in France; however, Strauss-Kahn could be charged for benefiting from misappropriated company funds if investigators conclude he attended sex sessions with prostitutes that company executives paid for out of expense accounts, according to Britain's The Guardian.

Sex scandal
Strauss-Kahn's job as head of the International Monetary Fund, as well as his presidential ambitions, came to an end last spring when he was accused of trying to rape a Guinean chambermaid in a Manhattan hotel suite. Criminal charges were later dropped when it emerged that the maid, Nafissatou Diallo, was an unreliable witness. Diallo is now pursuing him in a civil action.

Separate attempted-rape accusations by a Parisian writer also were shelved by French police on October 13 -- three days before Strauss-Kahn's name surfaced again in the Lille investigation.

Nancy Ing from NBC News and Reuters contributed to this report.

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A 10-man police force is hunting down the husband of a teen bride who was tortured and locked away in a toilet by her in-laws for months after she refused to become a prostitute, Afghan officials told the BBC.

"This is incredibly serious and not acceptable and all those responsible will be brought in to make an example to others," an Interior Ministry spokesman told the BBC on Tuesday.

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Sahar Gul, 15, was in critical condition when she was rescued from a house in Afghanistan’s northern Baghlan province last week, after her neighbors reported hearing her crying and moaning in pain.

The case has shocked Afghanistan, though rights activists say serious abuses against women and girls in the ultra-conservative society are common. President Hamid Karzai has said that whoever used violence against Gul will be punished.

Her mother-in-law and sister-in-law were arrested, but her husband, Ghulam Sakhi, 30, has eluded authorities, Interior Ministry spokesman Sediq Sediqi said.

Sakhi was identified as a soldier in the Afghan National Army who served in Helmand Province, The New York Times reported.

'One of the worst cases'
According to officials in northeastern Baghlan province, Gul's in-laws kept the girl in a basement for six months, ripped her fingernails out, tortured her with hot irons and broke her fingers. 

"She was married seven months ago, and was originally from Badakhshan province. Her in-laws tried to force her into prostitution to earn money," Rahima Zarifi, head of women's affairs in Baghlan, told Reuters.

Gul was covered in scars and bruises, with one eye still swollen shut six days after her rescue. She was being treated in a government hospital in Kabul, but her recovery needed extensive care and she may have to be sent to India, doctors said.

"This is one of the worst cases of violence against Afghan women. The perpetrators must be punished so others learn a lesson," health minister Suraya Dalil told journalists after meeting with the victim last week.

"This is an un-Islamic and inhuman act,” Baghlan governor, Munshi Abdul Majid, told The New York Times. 

Distressing chapter in Afghan culture
Despite progress in women's rights and freedom since the fall of the Taliban a decade ago, women throughout the country are still at risk of abduction, rape, forced marriage and being traded as commodity.

It can be difficult for women to escape violent situations at home, because of relentless social and sometimes legal pressure to stay in marriages.

Running away from an abusive husband is considered a "moral crime," for which women can be imprisoned in Afghanistan.

Some rape victims have also been imprisoned, because sex outside marriage, even when the woman is forced, is considered adultery, another "moral crime."

Msnbc.com's Sevil Omer and Reuters contributed to this report. 

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