Obama: Agents in Trouble Are 'Knuckleheads'

President Barack Obama defended the Secret Service on Tuesday, saying the employees at the center of the prostitution scandal were "knuckleheads" not representative of the agency that protects his family in the glare of public life.

But even as he spoke, officials on Capitol Hill were probing for any misconduct in the agency in the past decade and girding for the first public accounting of the incident that embarrassed the Obama administration.

For his part, Obama acknowledged Tuesday that the scandal was "a little distracting" and pressed for perspective.

"These guys are incredible. They protect me. They protect Michelle. They protect the girls. They protect our officials all around the world," the president said on NBC's "Late Night with Jimmy Fallon."

"A couple of knuckleheads shouldn't detract from what they do," Obama added. "What these guys were thinking, I don't know. That's why they're not there anymore."

A dozen Secret Service personnel and another 12 military enlistees preparing for Obama's visit to Cartagena, Colombia, are being investigated for cavorting with prostitutes. Six Secret Service agents have been let go over the incident and the Defense Department has suspended the security clearances of the military personnel being investigated.

As many as 20 prostitutes were involved with the group, officials say, and none are believed to be underage.

The incident broke into public view when one of the prostitutes argued with a Secret Service agent over her payment in a hallway of the Caribe hotel. Local law enforcement intervened on the prostitute's behalf. Paid sex is legal in Cartagena, but violates codes of conduct for U.S. personnel who were working there.

The scandal was widely denounced by official Washington, but it's a delicate political matter in an election year with the presidency and congressional majorities at stake. All sides have praised Secret Service Director Mark Sullivan's swift action and thorough investigation, in part because he's spent significant time keeping key lawmakers in the loop. Pentagon officials too are investigating and are expected to brief Senate Armed Services Committee Chairman Carl Levin and ranking Republican John McCain on Wednesday.

Even so, at least four congressional committees are investigating on the grounds that letting foreign nationals near U.S. personnel with sensitive information about the president's visit is a national security risk. Department of Homeland Security Secretary Janet Napolitano is expected Wednesday to face tough questions from the Senate Judiciary Committee on such matters as whether the agency's inspector general has launched an independent investigation.

Another Senate panel is looking for a pattern of misconduct. Sen. Joe Lieberman, chairman of the Homeland Security and Governmental Affairs Committee, told reporters on Tuesday that he'll hold hearings on the service's culture and whether clear rules exist on how agents should behave when they are off duty but on assignment.

"I mean you think they wouldn't need that but maybe they do," Lieberman said. He added that his investigators are taking a longer view and beginning to follow up on tips that "whistleblower people" have called in. He declined to provide details.

"I want to ask questions about whether there is any other evidence of misconduct by Secret Service agents in the last five or 10 years," Lieberman said. "If so what was done about it, could something have been done to have prevented what happened in Cartagena? And now that it has happened, what do they intend to do?"