WASHINGTON - The US Secret Service said on Saturday it put 11 agents on administrative leave to investigate their alleged misconduct before US President Barack Obama's trip to a Colombia summit, and apologized for the distraction the incident had caused.

"This is standard procedure and allows us the opportunity to conduct a full, thorough and fair investigation into the allegations," it said in a statement, without giving any details of what occurred. A Colombian police source and The Washington Post said prostitutes were involved.

"This incident is not reflective of the behavior of our personnel as they travel every day throughout the country and the world performing their duties in a dedicated, professional manner," the Secret Service said. "We regret any distraction from the Summit of the Americas this situation has caused."

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