3 in Scandal Being Forced Out of Secret Service, Officials Say

The agency has begun proceedings to fire one supervisor, and another has decided to retire, it said in a written statement. Another employee has resigned, and eight others remain under investigation.

“These guys have the clearest cases,” said a government official briefed on the investigation, referring to the three who are being pushed out.

The supervisor whom the Secret Service has begun proceedings to fire has threatened to sue the agency, the person said.

In its statement, the Secret Service said that it was “utilizing all investigative techniques available,” including polygraph examinations, and that investigators were interviewing agency employees and witnesses in Colombia.

Only one of the people under investigation has agreed to take the lie detector test, the government official said.

Among the people investigators for the Secret Service have interviewed are the maids who cleaned the rooms of the personnel during their stay, according to a Congressional staffer briefed on the investigation, who said that despite published reports, the maids said they had found no drug paraphernalia.

The Congressional staffer and government official spoke on the condition of anonymity because they did not want to jeopardize their access to sensitive information.

On Wednesday, Representative Peter T. King, the chairman of the House Committee on Homeland Security, praised the director of the Secret Service, Mark J. Sullivan, for moving swiftly with the investigation.

“I fully support what Mark is doing,” said Mr. King, a Republican from New York. “I talked to him yesterday and today, and I know that he wanted to take strong action once he had a legal basis. This is firm, decisive leadership. He has told me from the start that he would take firm action as soon as he could.”

The Secret Service has also expanded its internal investigation into whether there was misconduct on other trips. So far, investigators have not uncovered anything similar to what apparently happened in Colombia.

The Secret Service opened an investigation into the alleged misconduct after officials learned that there had been a dispute between a prostitute and a Secret Service agent over money and that other personnel may have been involved with prostitutes. High-ranking agency officials ordered 11 individuals to return to the United States, where they have faced questioning.

On Capitol Hill, Representative Darrell Issa, the chairman of the House Committee on Oversight and Government Reform, continued his criticism of the Secret Service.

In a letter to Mr. Sullivan, Mr. Issa, a Republican from California, and the ranking Democrat on the committee, Representative Elijah E. Cummings of Maryland, said the Secret Service personnel in Colombia had brought “foreign nationals into contact with sensitive security information” and were potentially exposed to “blackmail and other forms of potential compromise.”

Mr. Issa and Mr. Cummings listed 10 requests for information that they wanted answered by May 1.

“Your swift and decisive action in response to this scandal has given us confidence that the agency will complete a thorough investigation and take steps to ensure that similar lapses in judgment will never again jeopardize the important work of the U.S. Secret Service,” the representatives said.