Washington (CNN) -- A member of the U.S. military assigned to the White House Communications Agency is under investigation in connection with alleged misconduct in Colombia, bringing to 12 the total number of military personnel being reviewed, officials said Monday.
One Defense Department official said the military member admitted to his leadership that he was involved in misconduct "of some kind" while in Colombia for the recent Summit of the Americas attended by President Barack Obama.
The agency is a non-White House office that provides the president with secure communications while he travels. It is staffed by members of the military who report through the Defense Information Systems Agency.
A total of 24 people -- 12 Secret Service members and 12 U.S. military members -- are under investigation in the alleged prostitution scandal that occurred before Obama arrived in Cartagena on April 13.
The controversy has embarrassed the nearly 150-year-old Secret Service, which protects the president and other top officials and investigates criminal activity. It also raised questions about a possible security breach immediately preceding Obama's visit.
Six Secret Service members have left their jobs in the wake of the incident in Cartagena, and one employee "has been cleared of serious misconduct but will face administrative action," the Secret Service said. Five other Secret Service employees are on administrative leave and have had their security clearances temporarily revoked.
In addition, the U.S. military is investigating 12 of its own service members for alleged misconduct.
Defense Secretary Leon Panetta said Monday that security clearances have been suspended for all all U.S. military personnel involved in the incident in Cartagena.
At the White House, Press Secretary Jay Carney said Monday that there was no evidence of any wrongdoing by White House staff or advance team members. When asked about the possibility of White House Communications Agency staff members being involved, Carney pointed out that they are members of the military.
Also Monday, a source familiar with the investigation said that one of the Secret Service agents linked to the prostitution scandal brought a woman back to the Hilton Cartagena, the same hotel where Obama later stayed, five days before the president's arrival.
The source was not certain whether money exchanged hands or whether the Secret Service member simply brought a woman he met -- a foreign national -- to the Hilton.
According to the source, the incident appeared to be separate from the one a few nights later that caused 11 other Secret Service members to be sent home for alleged heavy drinking and consorting with prostitutes.
Based on the investigation, there is no evidence that the women realized the Secret Service personnel were with the agency, the source said. Investigators have interviewed the prostitutes and other women involved.
"It doesn't appear these women knew who the heck they were," the source said.
Meanwhile, House Homeland Security Chairman Peter King said he expects more Secret Service members to be forced out soon.
"I am very certain that within the next day or so, you're going to see a number of people leaving the Secret Service," said King, R-New York.
King, as well as the other source familiar with the investigation, said polygraph tests administered to the Secret Service members helped get information to force out six of them.
According to King, the 11 Secret Service members originally under investigation were all given drug tests, which came back negative.
From the start, Secret Service Director Mark Sullivan told legislators how outraged he was about the scandal, promising a broad and comprehensive investigation.
Most legislators seemed comfortable with the way the Secret Service has reacted to the scandal. However, both the House and Senate Homeland Security Committee chairmen are now conducting their own investigations and will probably hold hearings in coming weeks.
In a letter Friday, the ranking Republican on the Senate Judiciary Committee asked the Secret Service about the potential involvement of White House staff in the scandal.
Sen. Chuck Grassley, R-Iowa, questioned Sullivan and Acting Inspector General Charles Edwards about whether they were investigating the possibility that the White House Communications Agency and the White House Office of Advance may be involved.
Grassley asked specifically whether the agency reserved rooms or shared them with White House staff members for operational matters.
Carney said Monday that the White House general counsel's office looked into the possibility, as a matter of due diligence, and found no evidence that members of the White House staff or advance team took part.
Last week, Carney took exception to criticism of the Obama administration by some Republicans, calling it an attempt to politicize the issue.
"It is preposterous to politicize the Secret Service," Carney said then when asked about comments by former Alaska Gov. Sarah Palin and other Republicans that the scandal indicated poor leadership by Obama. "What they're doing is trying to turn these incidents, one that's still under investigation, into political advantage."
Sullivan -- who briefed Obama on the investigation Friday, according to White House officials -- has ordered a "comprehensive" investigation of everything that happened during the trip.
That includes interviews with every Secret Service member on site, hotel staff and alleged prostitutes, a source said Friday.
The 11 Secret Service employees accused of consorting with prostitutes arrived earlier the same day as a part of the "jump team" that flies in on military transport planes with vehicles in the president's motorcade.
According to sources, the alleged prostitutes -- the youngest of whom were in their early 20s -- signed in at the Cartagena hotel where Secret Service members apparently stayed, flashing their local ID cards.
One of these women allegedly was later involved in a dispute about how much she was to be paid for the night, which brought the entire incident to light and sparked controversy in the United States and Colombia.
Former Colombian President Alvaro Uribe said Thursday that the incident was due entirely to "a lack of ethics (on the part of) the Secret Service of the United States."
Members of the U.S. Congress offered similarly biting remarks. House Minority Leader Nancy Pelosi called the allegations "disgusting," while Senate Majority Leader Harry Reid described the agents' alleged actions as "either really stupid or a total lack of common sense."
While soliciting prostitution is in most cases legal for adults in Colombia, military law bars service members from patronizing prostitutes, engaging in conduct unbecoming an officer or, for enlisted personnel, conduct "prejudicial to good order and discipline." It is also considered a breach of the Secret Service's conduct code, government sources said.