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Members of elite Secret Service unit among those suspended in Colombia

Dan Emmett, a former Secret Service agent and author, NBC News' Michael Isikoff and Washington Post's Dana Milbank discuss the unfolding scandal in Colombia in which members of the service allegedly procured prostitutes.

Two Secret Service supervisors and three members of the agency's elite Counter-Assault Teams were among the 11 agents sent back from Colombia and placed on administrative leave over allegations that they brought prostitutes to their hotel rooms in Cartagena, law enforcement officials tell NBC News.

The involvement of Counter-Assault Team (CAT) members-- who are not members of the Uniformed Division, but full-fledged Secret Service agents -- ratchets up the seriousness of the incident, officials said.  The heavily armed agents play a key role in protecting the president, serving as part of any presidential motorcade, usually a few cars back from the president's. Their responsibility is to "neutralize" any attack "as quickly as possible," according to the Secret Service website.

"Their job is to fend off a heavy assault on the motorcade to give POTUS a chance to flee to a safe locale," one law enforcement source familiar with the investigation told NBC News, speaking on condition of anonymity.

The source said the two of the CAT team members were directly involved in the dispute with one of the prostitutes at the Hotel Caribe that led to the scandal. After bringing back the prostitute to their hotel room, the agents reportedly got into a dispute with one of the women when she complained she hadn’t been paid. The woman then went to the Colombian police -- who reported the matter to the U.S. Embassy.

Others involved in the incident include three members of the Secret Service Counter-Sniper Team, which is part of the Uniformed Division.

The source also said the incident raised the possibility of a potential security breach, telling NBC News that all Secret Service personnel had been given copies of the president's schedule, which they are told to lock up in a safe in their hotel rooms.

Michael Isikoff is an NBC News national investigative correspondent.