(CBS News) WASHINGTON -- The Secret Service sex scandal keeps expanding. The investigation now includes 24 Secret Service and military personnel.
But the White House now says it has conducted its own investigation and is confident that none of its own staffers was involved.
"Simply out of due diligence," White House Press Secretary Jay Carney says, "over the last several days, that review was conducted, and it produced no indication of any, any misconduct."
The White House says the internal probe was led by its counsel's office. It came amid calls by some lawmakers for the executive branch to account for the actions of its people in Colombia, where the scandal unfolded.
"There are no, to my knowledge, and have been no credible or specific allegations of misconduct by any member of the White House advance team or White House staff," Carney said.
But one senator argued that the in-house review may not be enough.
"I think," says Iowa Republican Charles Grassley, "it would substantiate what they're trying to say and give a great deal of credibility to it if they, if we knew that it was going to be reviewed by somebody outside the White House."
Grassley submitted a list of 14 questions about the White House investigation that he wants answered right away.
On Monday, another member of the military was implicated in the incident, bringing to 12 the number of armed services personnel being investigated.
That's in addition to the 12 Secret Service employees implicated in a night of drunken revelry and solicitation of prostitutes in Cartagena prior to President Obama's arrival.
"We expect our people, wherever they are, to abide by the highest standards of conduct," Defense Secretary Leon Panetta says.
Traveling to Colombia Monday on a trip unrelated to the scandal, Panetta said the service members under investigation who had security clearances have had them suspended, pending the outcome of the probe.
"Frankly," he said, "my biggest concern is the issue of security and what, what could possibly have been jeopardized by virtue of this kind of behavior."
To see Bill Plante's report, click on the video in the player above.