President Obama spoke about the Secret Service Colombian prostitute scandal for the first time since returning from Cartagena, calling most agents' work incredible and those involved in the scandal knuckleheads.

"The secret service, these guys are incredible," the president said. "So a couple of knuckleheads shouldn't detract from what they do but what these guys were thinking I don't know. That's why they're not there anymore."

Mr. Obama made the comments during a taping of the NBC talk show "Late Night with Jimmy Fallon" on the campus of the University of North Carolina at Chapel Hill where he gave a speech on student loan interest rates.

Asked about the scandal that overshadowed the president's trip to Colombia for the Summit of the Americas, President Obama noted the majority of Secret Service agents do a great job protecting him and his family.

"They protect me. They protect Michelle. They protect our girls," he said. "They protect our officials all around the world. 99.9 percent of them every day, they put their life on the line. They do a great job."

A dozen Secret Service agents as well as 12 military personnel have been accused of taking part in the scandal in which Colombian prostitutes were taken back to Cartagena hotel rooms by agents and military personnel who were in the country in advance of the president's trip earlier this month. When one prostitute complained she wasn't paid, the altercation spilled into hotel hallways and Colombian police became involved.

The White House says it conducted an internal review to make sure its advance staff was not involved.  Press Secretary Jay Carney reiterated Tuesday that the White House counsel found that no staff had a part in any wrongdoing.