The Obama administration looked Wednesday to minimize the Colombia prostitution scandal engulfing the Secret Service and the Defense Department as a few bad apples even as some lawmakers expressed new frustrations with the level of information they are getting.

“Ninety-nine percent of the men and women who work in the Secret Service are absolute professionals who do an extraordinary job protecting the president, protecting his family, protecting others,” White House Press Secretary Jay Carney said Wednesday.

Obama himself told late-night TV show host Jimmy Fallon on Tuesday that “a couple of knuckleheads shouldn’t detract from what they do. What they were thinking, I don’t know. That’s why they’re not there anymore.”

Homeland Security Secretary Janet Napolitano told the Senate Judiciary Committee on Wednesday that the internal investigation “will leave no stone unturned.”

All 12 Secret Service personnel accused of soliciting prostitutes during their work in advance of the president’s trip to Cartagena, Colombia, two weeks ago have already been dealt with, she said. Eight have left the agency, three face administrative action, and another will lose his security clearance. The investigation hasn’t turned up evidence of prior incidents yet, she said.

“We will not allow the actions of a few to tarnish the proud legacy of the Secret Service,” she said. Napolitano also said she had no knowledge of involvement by anyone working at the White House.

But Republicans are far from satisfied. Senate Armed Services ranking member John McCain (R-Ariz.) ripped the Defense Department Wednesday after receiving a briefing with “appallingly little new information” about the investigation into the prostitution scandal, which also involves a number of military service members.

McCain said he and Armed Services Chairman Carl Levin (D-Mich.) asked for the briefing to inquire about the national security implications from the incident in Cartagena.

“Unfortunately, nearly two weeks after the events in Colombia, the briefers sent by the Department of Defense were woefully unprepared to answer even the most basic questions about what happened in Cartagena and provided appallingly little new information other than the mechanics and timeline of the ongoing investigation,” McCain said in a statement. “The Department of Defense briefers did not even know the date the president arrived or the name of the senior military commander on the ground in Cartagena.”

McCain called the briefing “entirely unacceptable” and the “most ridiculous” he’s ever received.

“We need to know the facts. We need to know the impact of this potential misconduct — which occurred less than a day, or perhaps hours, before the president arrived in Cartagena — on the performance of the military Joint Task Force charged with his security.”

Levin also called the briefing “inadequate” and expressed surprise that the briefers didn’t know the names of the investigators in Colombia. Levin said that they were told that the investigation would be completed next week and scheduled another briefing for the following Monday.

Levin said he’s been unhappy with the department’s consultation with Congress in general and wants to talk to Defense Secretary Leon Panetta “as soon as possible” about improving communication with Congress. Levin also mentioned a recent press report on a new investigative unit at the Defense Department as something that he was surprised to hear about.

According to the Associated Press, the Pentagon has told lawmakers that it knew of six military personnel who had broken curfew rules prior to Obama’s arrival in Colombia but that the military allowed them to keep working.

Sen. Chuck Grassley (R-Iowa), meanwhile, has continued to press the White House for more details of its internal review of White House advance staff. Carney has declined to say how the review was conducted but that there was no indication of wrongdoing.

In questioning Napolitano on Wednesday, Grassley questioned the thoroughness of all three investigations: “I want to know if the inspector general is truly conducting an independent and impartial investigation. I think the same independent investigation is necessary from the inspector general and defense, and from the White House, to get to the bottom of the story for all of the advance team staff that was in Colombia.”

But Senate Homeland Security and Govermental Affairs Chairman Joe Lieberman (I-Conn.) dismissed the concerns about the White House’s internal investigation.

“The White House put out statement that the counsel had completed an investigation and that satisfies me,” he said. “The White House has every reason to do a thorough investigation because if it is found out … that the White House missed something, it’s going to be very embarrassing.”

Republicans and Democrats have generally praised Secret Service Director Mark Sullivan’s handling of the investigation, noting his frequent contact with lawmakers. Lieberman said Sullivan told him Wednesday that he has 50 more people to interview.

And Sen. Tom Harkin (D-Iowa) said Tuesday that with all of the issues the Senate faces, “hookers in Cartagena” are very low on his list of priorities.

Humberto Sanchez contributed to this report.