Story highlights Three more Secret Service employees have "chosen to resign," the agency says

A 12th Secret Service employee is "implicated," the agency says

The Secret Service chief briefs Obama about the probe, officials say

11 U.S. military service members are also being probed in the prostitution scandal

Three more Secret Service employees have "chosen to resign" in the wake of a prostitution scandal that emerged last week, the agency said in a news release Friday.

Six Secret Service members now have left their jobs in the wake of the incident in Cartagena, Colombia, which came while they were on a security detail in advance of President Barack Obama's trip there for the Summit of the Americas.

The agency also announced Friday that a 12th Secret Service "employee has been implicated," having previously said 11 were under investigation.

One employee "has been cleared of serious misconduct, but will face administrative action," the Secret Service said.

Five employees are on administrative leave and have had their security clearances temporarily revoked.

In addition, the U.S. military is investigating 11 of its own troops for possible heavy drinking and consorting with prostitutes.

A source close to the investigation said Secret Service Director Mark 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.

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That includes interviews with every Secret Service member on site, hotel staff and alleged prostitutes, the source said. In addition, the source confirmed that Secret Service agents were staying at a second hotel on the trip -- identified as a Hilton in Cartagena -- which presumably will be included in the expanded probe.

The controversy has embarrassed the nearly 150-year-old agency that 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, though House Homeland Security Committee Chairman Rep. Peter King has said that "from everything we know, nothing was compromised."

Two of the Secret Service employees whose departures were previously announced -- identified as David Chaney and Greg Stokes, a source familiar with the investigation told CNN national security contributor Fran Townsend -- were supervisors.

In a photo posted on his public Facebook page in January 2009, Chaney is seen standing behind Sarah Palin, wearing dark glasses and what appears be a wedding ring. Under the photo, Chaney posted a comment that said, "I was really checking her out, if you know what I mean?"

That remark drew a strong response Thursday night from Palin, who was a vice presidential candidate when the photo was taken.

"This agent who was kind of ridiculous there in posting pictures and comments about checking someone out," Palin said on Fox News. "Check this out, bodyguard. You're fired! And I hope his wife sends him to the doghouse."

Chaney, a son of a Secret Service agent, has been employed with the agency since 1987, according to his posting on Reunion.com. The posting notes that he is married, has an adopted son and his assignments included a stint protecting former Vice President Dick Cheney.

Stokes supervised the canine training unit at the Secret Service's James J. Rowley Training Center outside Washington, according to PetLife Radio and a career development posting on the University of Maryland's website.

Attorney Lawrence Berger -- general counsel for the Federal Law Enforcement Officers Association, which represents Secret Service agents and others -- said he is not representing all of the agents involved in the Colombia story, but he does have several other clients in the group in addition to Chaney and Stokes.

He would not comment on specifics of the investigation, but complained about leaks that publicly identified Chaney and Stokes and gave details of what allegedly happened in Colombia.

"The concern I have is about illegal leaks coming from apparently rogue elements within the Secret Service of privacy-protected information," Berger said. "It is distorting the review of what happened."

All the employees are accused of bringing prostitutes to Cartagena's Hotel El Caribe ahead of last week's visit by Obama. They'd arrived earlier that morning as a part of the "jump team" that flies in on military transport planes with vehicles in the president's motorcade, said Townsend.

According to sources, the alleged prostitutes -- the youngest of whom were in their early 20s -- signed in at the 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 told CNN on 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."

The U.S. military is investigating six members of its elite Army Special Forces, or Green Berets, officials said.

The Green Berets' failure to make curfew the night of the incident involving the Secret Service agents led the military to start its investigation, a U.S. official told CNN.

All the military personnel are being investigated for heavy drinking and use of prostitutes while in Colombia as part of the support team for Obama's visit, the official said. They are not likely to redeploy until the matter is resolved, other military officials said.

The military investigation could end with no action, administrative action such as a letter of reprimand or a recommendation to proceed with criminal charges, officials said.

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.