Munir Uz Zaman / AFP - Getty Images

Bangladeshi volunteers and rescue workers search for survivors at the scene of an eight-story building collapse in Savar, on the outskirts of Dhaka, Bangladesh on Thursday.

DHAKA, Bangladesh -- Survivors from a building that collapsed in Bangladesh killing more than 250 mainly women workers described hearing a deafening crack before the complex housing factories supplying Western clothes retailers crashed down in a matter of seconds.

Dozens more victims were thought to be still trapped in the rubble after the disaster, which comes five months after a factory fire killed 112 people. The tragedy could further hurt Bangladesh's reputation as a source of low-cost goods for European and North American firms.

Local residents helped pull survivors from the twisted wreckage of the eight-story Rana Plaza building which collapsed on Wednesday in Savar, 20 miles outside the capital Dhaka. More than 1,000 people were injured.

Relatives identified their dead among rows of corpses.

"An unspecified number of victims are still trapped," said Mizanur Rahman, a rescue worker with the fire brigade, as he clambered over the wreckage. "We can't be certain of getting them all out alive. We are losing a bit of hope."

Dhaka's district police chief Habibur Rahman said the death toll could rise further.

"I was at work on the third floor, and then suddenly I heard a deafening sound, but couldn't understand what was happening," said factory worker Zohra Begum. "I ran and was hit by something on my head."

The government declared a national day of mourning and flags were flown half-staff at all official buildings.

Dhaka city development authority had filed a case against the building's owner for faulty construction, police chief Rahman said. It filed another case against the owner and the five garments factories for causing unlawful death.

Images: Desperate search for survivors

Bangladesh Garment Manufacturers and Exporters Association (BGMEA) President Mohammad Atiqul Islam said there were 3,122 workers in the factories on Wednesday. He said there had been indications from local officials that cracks had been found in the building the day before.

"We asked the garment owners to keep it closed," Islam said.

Rana Plaza's owner had told proprietors of the building's five garment factories that the cracks were not dangerous, Islam added. "After getting the green signal from the plaza owner all the garment factories opened," he said.

However, police official Mohammad Asaduzzaman said factory owners appeared to have ignored a warning not to allow their workers into the building after a crack was detected on Tuesday.

More than 1,000 textile workers besieged the BGMEA offices on Thursday, pelting it with stones and clashing with riot police, TV channels showed. The workers demanded all garment factories be shut and the owners harshly punished for accidents.

Mohammad Mosharraf, who was rescued on Thursday after 26 hours, said he had been hit on the head by something heavy and knocked unconscious when the building came down.

"When I regain my sense I found another four colleagues are also trapped under the debris of the building," he told Reuters. "We desperately tried to shout for someone to rescue us. Initially we didn't receive any response, but we moved to another part of the floor and found some light and heard voices."

Munir Uz Zaman / AFP - Getty Images

A Bangladeshi woman reacts after identifying the body of her husband at scene of a collapsed building in Savar, on the outskirts of Dhaka, Bangladesh on Thursday.

The Rana Plaza building collapse follows a fire at the Tazreen Fashion factory on the outskirts of Dhaka that killed 112 people in November and another incident at a factory in January in which seven people died, compounding concerns about worker safety and low wages in Bangladesh.

U.K. clothing retailer Primark confirmed that one of its suppliers occupied the second floor of the building.

Canada's Loblaw, a unit of food processing and distribution firm George Weston Ltd, also confirmed a connection with the building. It said one factory made a small number of "Joe Fresh" apparel items for the company.

Documents including order sheets and cutting plans obtained by Reuters appeared to show that other major clothing brands such as Spain's Mango and Benetton had used suppliers in the building in the last year. A Benetton spokesman said none of the factories were suppliers to the company.

About 3.6 million people work in Bangladesh's garment industry, making it the world's second-largest apparel exporter.

Wal-Mart said on Wednesday it had not determined whether a factory in the building that collapsed was producing goods for the company.

DHAKA, Bangladesh -- Thousands of Bangladeshi workers blocked the streets of a Dhaka suburb Monday, throwing stones at factories and smashing vehicles, as they demanded justice for at least 112 people killed in a garment-factory fire that highlighted unsafe conditions in an industry rushing to produce for major retailers around the world.

Another fire broke out in a multi-story garment factory in a Dhaka suburb on Monday, but a fire department official said the blaze was under control and there were no immediate reports that anyone had died in the latest blaze.

Some 200 factories were closed for the day after the protest erupted in Savar, the industrial zone where Saturday's deadly fire occurred. Protesters blocked a major highway.

Andrew Biraj / Reuters

Workers shout slogans Monday as they protest against the death of their colleagues after a weekend fire in a garment factory in Savar, Bangladesh, killed more than 100 people.

The government announced that Tuesday will be a day of national mourning, with the national flag flying at half-mast in honor of the dead.

Fire official: No emergency exit
Investigators suspect that a short circuit caused the fire, said Maj. Mohammad Mahbub, fire department operations director. But he said it was not the fire itself but the lack of safety measures in the eight-story building that made it so deadly.

Fire sweeps clothing factory in Bangladesh -- more than 100 killed

"Had there been at least one emergency exit through outside the factory, the casualties would have been much lower," Mahbub said.

He said firefighters recovered at least 100 bodies from the factory, and 12 more people died at hospitals after jumping from the building to escape the fire.

Local media reported that up to 124 people were killed.

"I haven't been able to find my mother," one worker, who gave her name as Shahida, told Reuters. "I demand justice. I demand that the owner be arrested."

Mohammad Ripu, a survivor, said Monday that he tried to run out of the building when the fire alarm rang but was stopped.

"Managers told us, 'Nothing happened. The fire alarm had just gone out of order. Go back to work,'" Ripu said. "But we quickly understood that there was a fire. As we again ran for the exit point we found it locked from outside, and it was too late."

Watch World News videos on NBCNews.com

Ripu said he jumped from a second-floor window and suffered minor injuries.

Mahbub said the fire broke out on the ground floor, which was used as a warehouse, and spread quickly to the upper floors. He said many workers who retreated to the roof were rescued, but dozens of others were trapped; firefighters recovered 69 bodies from the second floor alone.

Many victims were burned beyond recognition. The bodies were laid out in rows at a school nearby. Many of them were handed over to families; unclaimed victims were taken to Dhaka Medical College for identification.

More news from South & Central Asia on NBCNews.com

Hazardous conditions are widespread
The garment-factory fire was Bangladesh's deadliest in recent memory, but such dangers have long been a fact of life as the industry has mushroomed to meet demand from major retailers around the world.

At least 500 people have died in clothing factory accidents in Bangladesh since 2006, according to fire department officials.

The Savar factory is owned by Tazreen Fashions Ltd., a subsidiary of the Tuba Group. Neither Tazreen nor Tuba Group officials could be reached for comment.

The Tuba Group is a major Bangladeshi garment exporter whose clients include Wal-Mart, Carrefour and IKEA, according to its website.

Andrew Biraj / Reuters

A firefighter inspects a garment factory in Savar, Bangladesh, on Sunday after a fire caused more than 100 deaths there a day earlier.

Bangladesh has some 4,000 garment factories, many without proper safety measures. The country annually earns about $20 billion from exports of garment products, mainly to the United States and Europe.

Complete World coverage on NBCNews.com

The Bangladesh Garment Manufacturers and Exporters Association said it would stand by the victims' families and offered $1,250 to each of the families of the dead. The association's acting president, Siddiqur Rahman, said on a talk show late Sunday that Tazreen's owner was to meet with group representatives on Monday.

"We will discuss what other things we can do for the families of the dead," Rahman said on Rtv, a private television station. "We are worried about what has happened. We hope to discuss everything in detail in that meeting."

The Associated Press and Reuters contributed to this report.

More world stories from NBC News:

• Egypt's Morsi says he wants to stabilize country
• More than 100 killed in Bangladesh factory fire
• Drug gang bust in Honduras nets $100M assets
• Irish editor who published pics of naked Kate Middleton resigns
• Scientists rush to save manta rays, the 'pandas of the ocean'
• Despite troubles at home, Egypt's Morsi is pivotal player in Mideast

Follow World News from NBCNews.com on Twitter and Facebook

All photos by Vivek Prakash / Reuters

Labourers sort through and grade harvested tomatoes on a farm that supplies fresh produce to Wal-Mart in Narayangaon, about 112 miles west of Mumbai.

Labourers harvest tomatoes on a farm that supplies fresh produce to Wal-Mart in Narayangaon.

Two-wheelers move past the newly opened Bharti Wal-Mart Best Price Modern wholesale store in the southern Indian city of Hyderabad.

Workers walk inside an aisle of the newly opened Bharti Wal-Mart Best Price Modern wholesale store.

Reuters reports that India requires Wal-mart to source 30 percent of its goods from local, small industries, and therefore plans to sign up 35,000 farmers in the next three years:

Wal-Mart must buy in small batches from small plot-holders in a country where more than 80 percent of farms are under 2 hectares. That means contracting with thousands of farmers will still yield only a few thousand metric tons. In North America, retailers like Wal-Mart can buy from a few hundred farmers who provide hundreds of thousands of metric tons of produce between them.

Follow @NBCNewsPictures

© Stringer Mexico / Reuters

A Wal-Mart store in Mexico City is shown. An extensive investigation by The New York Times into an alleged bribery effort by top executives at Wal-Mart's Mexican subsidiary could be very costly for the discount retailer, legal and retail experts said Monday.

Revelations about an alleged bribery effort and cover-up by top executives at Wal-Mart’s Mexican subsidiary could be very costly for the world's biggest retailer, legal and retail experts said Monday.

A New York Times article published over the weekend said executives deliberately obstructed an internal probe into bribery at Wal-Mart de Mexico, the company's largest international division.

The allegations, if proven true, could badly hamper the company and its management for years. They could lead to a time-consuming global probe, substantial financial penalties imposed by U.S. authorities and the departure of some executives, experts said.

“We could easily see criminal prosecutions,” said Jacob Frenkel, a former official of the Securities and Exchange Commission.

“The fact that it’s a U.S. company working through a Mexican subsidiary does not give the U.S. company protection,” Frenkel told CNBC, adding that anyone who is found to have their fingerprints on the alleged wrongdoings “has potential liability, civilly and criminally.”

Frenkel said he wouldn’t rule out potential jail time for Wal-Mart executives and estimated that the financial consequences of the Times report, if accurate, could cost Wal-Mart $1 billion in settlements and internal investigations.

Wal-Mart shares (WMT) fell nearly 5 percent Monday.

Frenkel added that he expects regulators to pursue any case against Wal-Mart vigorously.

“The Department of Justice has placed a high premium on investigating and prosecuting violations of what is basically our bribery law,” he said.

The allegations could also cost Wal-Mart in terms of its future growth, said Deutsche Bank retail analyst Charles Grom.

“It would put a broadside in the growth engine of the company,” he said. “Unlike prior bad PR stories in recent years, this will be a material distraction for Wal-Mart on multiple fronts.”

BMO Capital Markets analyst Wayne Hood said in a research note that the allegations could hamper the discount chain’s future growth both domestically and abroad.

“Articles like this will be used against the company by activists and competitors when it attempts to open stores in the U.S. and abroad,” Hood wrote.

In a new twist in the story Monday, two Democratic lawmakers said they are launching an investigation into allegations of bribery at Wal-Mart Stores Inc's Mexican affiliate.

Representative Elijah Cummings, the top Democrat on the House Oversight and Government Reform Committee, and Representative Henry Waxman, the top Democrat on the House Energy and Commerce Committee, sent a letter to Wal-Mart Chief Executive Michael Duke, requesting an in-person meeting with company officials.

The lawmakers also said they are contacting former Wal-Mart executives who may have documents or information relevant to a congressional investigation.

If the Times report is true, it means the company is at risk of being charged under the 1977 Foreign Corrupt Practices Act (FCPA), which prohibits the bribing of foreign officials to get business abroad.

A number of big companies have disclosed potential liabilities under the act in their financial statements to investors, including Alcoa, Avon, Marathon Oil, Kraft Foods and Hewlett-Packard.

One of the largest-ever Foreign Corrupt Practices Act case involved Siemens AG. In 2008, the electronics and electrical engineering company paid a $450 million fine over allegations its executives and agents made payments totaling approximately $1.4 billion to bribe overseas officials in turn for business.

“Wal-Mart has a squeaky-clean image when it comes to these sorts of things, so I’m quite surprised they would try to sweep in under the carpet,” Patrick McKeever, a senior equity analyst at MKM Partners, told CNBC.

McKeever noted that much of Wal-Mart’s recent growth has come from opening stores overseas, and so any increased regulatory scrutiny on its international operations could hinder the company's overall growth.

He also said Wal-Mart’s statement on the bribery allegations “didn’t do the company any favors,” as it didn’t refute the allegations against the company, and so allowed for the possibility that they are true.

In the 10 years he has covered Wal-Mart as a stock analyst, “this is by far the most damaging story,” he said. “It’s a big deal.”

One option Wal-Mart will have is to remove some executives involved in the alleged bribery or cover-up as this could make it easier to reach an out-of-court settlement with the Department of Justice.

“Among the remedial actions is ‘house cleaning’ of anyone involved in illegal conduct,” said Richard Cassin, a lawyer who is an expert on the FCPA and writes a blog about it.

“If a company can say those involved in the questionable conduct are already gone, the DOJ is likely to look more favorably on the company and current management.”

Wal-Mart said it had disclosed its probe to the DOJ and SEC. The company also said it had taken steps at the Mexico unit, known as Walmex, to boost internal controls to make sure it was compliant with the FCPA.

But, according to the Times, the disclosure came only after the newspaper informed Wal-Mart that it was looking into the bribery allegations, years after the bribes were said to first come to management's attention.

According to the Times, Wal-Mart Chief Executive Mike Duke and former CEO Lee Scott, who still sits on the company's board, were among senior executives allegedly aware of the situation. Duke was put in charge of Wal-Mart's international division in 2005.

Some retail experts said they thought that Wal-Mart would be unlikely to sacrifice Duke in the investigation and any related settlement talks with the government.

“I don’t get the sense that Mike Duke's going to lose his job over this,” said Joseph Feldman, senior retail analyst at Telsey Advisory Group. “I think that they'll try to put the spin on it that they have been putting on it -- that it happened years ago, they rooted it out and it doesn't happen anymore.”

The Wal-Mart allegations will undoubtedly leave a black mark on the company’s name, said Yale School of Management corporate governance expert Jeffrey Sonnenfeld.

“This is a great global company, and it didn’t have to cheat to win,” Sonnenfeld told CNBC.

“A company’s reputation is worth a lot,” he said. “Great companies in the past -- Johnson & Johnson, UPS -- they know there’s a great value in having this sense of cleanliness and a reputation that stands for something beyond what you think you can get away with.”

Wal-Mart reported consolidated net income of $16.4 billion for the year ended Jan. 31, 2012, down 3.6 percent from the same period the year before.

Reuters contributed to this report.

Will the bribery allegations hurt Wal-Mart? Discuss it on Facebook.