By Susan Cornwell
WASHINGTON (Reuters) - The Secret Service is "scrubbing" its files for past incidents involving agents like last week's alleged misconduct with prostitutes at a Colombia hotel, a Republican senator said on Wednesday.
U.S. Senator Susan Collins said she told Secret Service director Mark Sullivan she found it hard to believe the episode was the only one of its kind, because "there were too many people involved."
"He said they were scrubbing the files and looking at whether there were any hints that there had been previous incidents," Collins told reporters outside the Senate.
Secret Service agents and military personnel took as many as 21 women back to their hotel in Colombia, according to Collins, marring President Barack Obama's weekend trip to the Summit of the Americas in the Colombian coastal city of Cartagena.
Collins, the ranking Republican on the Senate Homeland Security Committee, spoke to Sullivan about the episode on Monday and Tuesday, when she pressed him to look into the files.
"Think of all the missions and countries that the Secret Service visits in advance of the president's trips," she said.
"I think they should look at disciplinary records, at whether supervisors were - had admonished (them) even informally," she said. "My instinct is that this was not one-time."
Another Republican lawmaker who spoke with Sullivan on Tuesday, Senator Charles Grassley, said Sullivan had asked him not to reveal whether polygraph tests were being offered to Secret Service agents under investigation.
Some news media have reported that polygraphs have been offered, and accepted by some of the agents.
"My concern is, is this a culture that goes beyond 11 people?" Grassley told reporters.
Details continued to emerge about the scandal. Under investigation are 11 Secret Service agents who have been placed on leave and had their security clearances revoked, as well as 10 U.S. military service members in Colombia.
The military service members being investigated are two Marine dog handlers, five Army Special Forces members, two Navy explosive-ordnance experts and one Air Force member, a U.S. official said.
The Americans brought prostitutes to their beachfront hotel before Obama arrived for the summit, according to a local police source in Colombia. But some of the Secret Service agents have said they did not think the women were prostitutes, according to U.S. Representative Peter King.
Collins said both the Secret Service and the U.S. military had investigators in Colombia interviewing the women who were brought to the hotel by the Americans.
King said on Tuesday the investigators had not found that the women were involved in the drug trade or organized crime.
Another concern is whether sensitive information was compromised by taking foreigners into agents' hotel rooms, Grassley said, but he believed adequate precautions appear to have been followed.
At least four congressional committees are looking into the events but no one has announced any hearings on the matter.
Senator John McCain, the ranking Republican on the Senate Armed Services Committee, said he and the panel's chairman, Senator Carl Levin, expected to get a briefing soon on the investigation from Pentagon chief Leon Panetta.
(Additional reporting by David Alexander)