WASHINGTON >> A week after a Secret Service prostitution scandal began unfolding in the hallway of a Colombian hotel, six agents have lost their jobs and hundreds of people have been interviewed.

The agency said Friday that three officers had resigned, days after two supervisors and another officer were forced out. Director Mark Sullivan briefed President Barack Obama in the Oval Office on the latest developments.

It all started when an argument over payment between a Secret Service agent and a Colombian prostitute spilled into the hallway of the Hotel Caribe, where a contingent of agents and military personnel were staying as part of a security detail in advance of the president’s arrival for last weekend’s the Summit of the Americas in Cartagena, Colombia.

A government official briefed on the investigation said more than 200 people have been interviewed so far. The official spoke on the condition of anonymity to discuss the continuing investigation.

Late Friday, Sen. Chuck Grassley, R-Iowa, urged a broader investigation, including checking hotel records for White House advance staff and communications personnel who were in Cartagena for the summit.

In a letter to Sullivan and the inspector general at the Homeland Security Department, Grassley asked whether hotel records for the White House staffers had been pulled as part of the investigations.

The scandal, which now includes 12 Secret Service employees and 11 military members, has become a political issue.

Sarah Palin, the Republican vice presidential nominee in 2008, weighed in after pictures from ousted Secret Service supervisor David Chaney’s Facebook profile emerged.

He joked about "really checking her out" after a friend comment on a picture of Palin, with Chaney standing in the background during the 2008 campaign.

Palin told Fox News that joke was on Chaney. "Well, check this out, buddy — you’re fired!" Palin said. She later said the scandal was a sign of "government run amok."

Obama’s spokesman has said it is "preposterous to politicize" the situation and has said Obama would be angry if allegations published so far proved to be true.

The incident in Colombia involved at least some Secret Service personnel bringing prostitutes to their hotel rooms.

News of the incident, which involves at least 20 Colombian women, broke a week ago after a fight over payment between a prostitute and a Secret Service agent spilled into the hotel hallway. A 24-year-old Colombian prostitute told The New York Times that the agent agreed to pay her $800 for a night of sex but the next morning offered her only $30. She eventually left the hotel, she told the newspaper, after she was paid $225.

All of the agents being investigated have had their top-secret clearances revoked.

Col. Scott Malcom, a spokesman for U.S. Southern Command, said the six soldiers, two Marines, two Navy personnel, and one Air Force airman have been sent home to their home duty stations. The soldiers are all from the 7th Special Forces Group, Airborne. The Marines and Navy personnel are from San Diego, and the Air Force member is from Charleston, S.C.

Maclom said the troops aren’t under any specific restrictions but have been required to stay at their home stations while the investigation continues. Malcom added that military investigators could return from Colombia as soon as this weekend.

The lawyer for Chaney and fellow supervisor Greg Stokes said Obama’s safety was never at risk, and criticized leaks of internal government investigations in the case, signaling a possible strategy for an upcoming legal defense.

Chaney and Stokes were forced out Wednesday. A third agent, who has not been identified and was not a supervisor, resigned.

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Associated Press writers Eileen Sullivan, Laurie Kellman, Robert Burns, Larry Margasak, Julie Pace, Anne Gearan in Washington, Nomaan Merchant in Dallas and Frank Bajak in Cartagena, Colombia, contributed to this report.