(CBS News) WASHINGTON - Sources told CBS News there have been incidents of Secret Service agents partying on the road before the one in Colombia that exploded into a scandal, though the previous ones may not have involved prostitutes.
The sources also said some of the agents pushed to retire in the wake of the the Colombia scandal may fight back, saying supervisors have been aware of past rule-breaking and done nothing.
As many as 50 more interviews are still to come as officials try to get to the bottom of the Colombia sex scandal.
Homeland Security Secretary Janet Napolitano, whose department is responsible for the Secret Service, assured senators Wednesday that the Secret Service investigation is continuing, even after nine agents lost, or could lose, their jobs in the wake of the scandal.
"We are going to get to the bottom of this," Napolitano said. "We are going to make sure that standards and training need to be tightened up are tightened."
As questions continue to rise over whether the Colombia scandal may not have been an isolated incident, senators pressed Napolitano for more information.
"To your knowledge," asked Sen. Pat Leahy, D-Vt., "is this the first time something like this has happened or have you reports of similar incidences in the past?"
"Over the past two-and-a-half years, the Secret Service Office of Professional Responsibility has not received any such complaint," she said.
And there are new questions about U.S. troops connected to the Colombia incident. It involved members of the U.S. military as well as the Secret Service and, while one group of senators questioned Napolitano Wednesday, others got a briefing from the military, and they're not happy.
"It was a waste of time because they had no information," Sen. John McCain, R-Ariz., said.
Pentagon officials filled the senators in on the status of the 12 U.S. troops implicated in the incident.
"I expressed my extreme dissatisfaction with the lack of any concrete information that was provided to us from a national security standpoint," McCain said.
The troops -- from the Army, Navy, Marine Corps and Air Force, including five members of special forces -- were working in Colombia in advance of the president's trip. Defense Secretary Leon Panetta has said that they have had their security clearances suspended and they could be revoked, but so far no further action has been taken.
To see Bill Plante's report, click on the video in the player above.