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.

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.

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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.

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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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