April 20, 2012 -- Three more Secret Service officials have resigned in connection with the Colombia prostitution scandal.

That makes a total of six agents who have left their jobs since the news broke that some members of the agency paid prostitutes while in Colombia in advance of President Obama's trip to Cartagena for the Summit of the Americas.

"In addition to the previously announced personnel actions, three additional employees have chosen to resign," Secret Service Assistant Director Paul S. Morrissey said in a statement. "As a result of the ongoing investigation in Cartagena, a twelfth employee has been implicated. He has been placed on administrative leave and his security clearance has been temporarily suspended pending the outcome of the investigation."

"One of the employees involved has been cleared of serious misconduct, but will face appropriate administrative action," Morrissey said. "At this point, five employees continue to be on administrative leave and their security clearances remain suspended pending the outcome of this investigation."

This afternoon, the president received an in-person briefing from Mark Sullivan, director of the Secret Service, in the Oval Office on the agency's ongoing investigation, a senior administration official tells ABC News.

The identities of two supervisors who lost their jobs were reported on Thursday, and another agent was leaving the agency voluntarily. The Washington Post reported that one of the supervisors, David Chaney, joked about Sarah Palin on his Facebook page during the 2008 campaign.

The other ousted supervisor, Greg Stokes, an agent in the K-9 unit, plans to come forward early next week to publicly challenge his dismissal from the Secret Service, a source tells ABC News.

White House press secretary Jay Carney said at his briefing with the press on Friday that he was not "in a position to answer questions" about whether the prostitutes came into contact with confidential information. He also said he's "not prepared to address" whether Sullivan's oversight has been insufficient.

Reports of the Secret Service and members of the military cavorting with prostitutes in Colombia broke around the same time that photos of American soldiers posing with the corpses and body parts of Afghan insurgents surfaced.

"It is preposterous to politicize the Secret Service, to politicize the behavior of the terrible conduct of some soldiers in Afghanistan in a war that's been going on for 10 years," Carney said. "On the face of it, it's a ridiculous assertion that trivializes both the very serious nature of the endeavor that our military is engaged in in Afghanistan and the very serious nature, both of the work that the Secret Service does, the apolitical nature of the institution."

Chaney reportedly once posted on Facebook a photo of himself on the job behind Palin during the 2008 campaign and wrote next to it, "I was really checking her out, if you know what i mean?"

Palin, always quick to fire back, used the friendly atmosphere on Fox News to rib the ex-agent — and criticize President Obama, too.

"Well, this agent, who was kind of ridiculous there in posting pictures and comments about checking someone out — well, check this out, bodyguard. You're fired," Palin said on Greta Van Susteren's show Thursday night. "And I hope his wife kicks his ocoli and sends him to the doghouse, as long as he's not eating the dog, along with his former boss."

Chaney's Facebook posting was reported by The Washington Post, which said the 48-year-old Secret Service veteran is married and has an adult son.

"It's our ultimate position that nothing they may or may not have done in Colombia negatively impacted the efficiency of their mission," the agents' lawyer, Lawrence Berger, told the paper. "Nothing that has been reported to have been done has impacted negatively their mission or the president's visit."

Berger told ABC News that he thinks a person in the Secret Service is violating privacy rules by leaking the agents' names to the media. A police officer outside Chaney's home in Ashburg, Va., said Thursday night that the family wouldn't be speaking.

Republicans have expressed concern that the operation in Colombia could have endangered President Obama, but they've also tried to tie him to the mismanagement of the agency as they simultaneously grill officials at the General Services Administration over a separate spending scandal in Las Vegas. House Speaker John Boehner's office circulated an AP story on Thursday that noted that both scandals, plus a controversy involving American soldiers posing with suicide bombers' bodies in Afghanistan, are obstructing Obama's agenda.

Two top House Republicans, Darrell Issa and Peter King, have led the charge in investigating the Secret Service agents' behavior.

"It's a symptom of government run amok, though, Greta. And it's, like, you know, who's minding the store around here?" Palin said Thursday night. "And when it comes to this particular issue of Secret Service, again, playing with the taxpayer's dime and playing with prostitutes and checking out those whom they are guarding. You know, the president, for one, he better be wary there of – when Secret Service is accompanying his family on vacation. They may be checking out the first lady instead of guarding her."

"And I say that not just tongue-in-cheek, but I say that seriously, that the president, the CEO of this operation called our federal government, has got to start cracking down on these agencies," she continued. "He is the head of the administrative branch and all these different departments in the administration that now people are seeing things that are so amiss within these departments."

ABC News has learned that some of the prostitutes who allegedly met with the agents in Colombia have been interviewed by investigators, but American officials are still looking for others.

Devin Dwyer and Lauren Pearle contributed to this report.