By Susan Cornwell

WASHINGTON (Reuters) - A congressional committee is considering sending investigators to Colombia in the coming weeks to gather information in an expanded probe of alleged Secret Service misconduct with prostitutes, the chairman said on Friday.

Representative Peter King, the Republican chairman of the House of Representatives Homeland Security Committee, said his staff will move to a "full-scale" investigation after it receives answers to 50 questions the panel posed to Secret Service Director Mark Sullivan about this month's incident.

Neither King nor another senior House lawmaker, Democratic Representative Elijah Cummings, said they saw a weakening of support for Sullivan in Congress despite reports of other Secret Service misbehavior.

"In my estimation, he is doing all he can do. ... Rumors are coming in and he's following each one of them, he's looking into every single rumor that comes in," Cummings told Reuters.

Cummings, the top Democrat on the House Oversight and Government Reform Committee, which also is looking into the matter, said Sullivan plans to have 100 top Secret Service employees participate in a "very intense" ethics course next week.

The congressman also said Sullivan told him that "from now on a member of the professional responsibility section would be accompanying folks on all (Secret Service) trips" and that each trip will include ethics briefings and a warning to agents not to bring prostitutes to their rooms.

The scandal over allegations that Secret Service agents and military personnel consorted with prostitutes in the coastal city of Cartagena erupted two weeks ago, just before President Barack Obama arrived for a visit to Colombia.

Twelve Secret Service employees were implicated in the Colombia matter. Eight have left the agency, three were cleared of serious misconduct and one is being stripped of his security clearance. Twelve members of the military were also implicated and that investigation is ongoing.

At least three other congressional panels are investigating the scandal, and one, the Senate Homeland Security Committee, plans hearings.

'MORALITY COP'

"I'm not into being a morality cop, but what happened in Colombia was clearly wrong because it put security at risk," King said outside the House chamber, adding that his committee "probably in the next few weeks" would send investigators to Colombia as part of the probe.

The Secret Service this week began looking into allegations of similar misbehavior before a 2011 presidential trip to El Salvador.

The Secret Service so far has not been able to validate the allegations about El Salvador made in a report Thursday by KIRO-TV news in Seattle, King said. The station is part of the CBS-Cox media group.

"They have gone through the trip file, and spoke with some of the people who were on the trip, the supervisors, and so far it's nothing," King said. "And they are talking to the reporter and trying to find out who his sources are."

In the KIRO report, an anonymous U.S. contractor described visiting a San Salvador strip club offering sexual favors with some Secret Service agents and U.S. military specialists in advance of Obama's March 2011 visit.

Reports that agents went to a raucous night club in Russia in 2000 are not being examined, King said, suggesting that there were no allegations of illegal conduct in connection with that alleged incident.

(Reporting By Susan Cornwell; Editing by Marilyn W. Thompson and Will Dunham)