Washington - The US Secret Service is moving quickly to quell a prostitution scandal that has given President Barack Obama's critics political ammunition, forcing three agents out of government less than a week after the embarrassing incident came to light.
Lawmakers welcomed the move but said more needed to be done.
"It's certainly not over," said Representative Peter King, Republican chair of the House Homeland Security Committee, which oversees the Secret Service.
The Secret Service did not identify the agents being forced out or eight more it said remain on administrative leave. In a statement, it said one supervisor was allowed to retire and another will be fired for cause. A third employee, who was not a supervisor, has resigned.
A person familiar with the Secret Service said the two supervisors forced out on Wednesday are both in the agency's uniformed division; one is a sergeant.
The team under investigation includes members of the agency's "jump teams", which are sent to sites ahead of the president's arrival. Others involved are on counter-assault and counter-sniper teams. The majority of those involved are likely to be based in the Washington area, the person familiar said.
Secret Service Director Mark Sullivan has offered the agents under investigation the chance to take a polygraph test, though the agents can refuse.
The person familiar with the agency spoke on the condition of anonymity in order to discuss
The agents were implicated in the prostitution scandal in Colombia that also involved about 10 military service members and as many as 20 women. All the Secret Service employees who were involved had their security clearances revoked.
The embarrassing scandal erupted last week after 11 Secret Service agents were sent home from Cartagena, on Colombia's Caribbean coast, after a night of partying that reportedly ended with at least some of them bringing prostitutes back to their hotel.
The special agents and uniformed officers were in Colombia in advance of Obama's arrival for the Summit of the Americas.
In Washington and Colombia, separate US government investigations are already under way. King said he has assigned four congressional investigators to the probe. The House Committee on Oversight and Government Reform, led by Representative Darrell Issa, a Republican, sought details of the Secret Service investigation, including the disciplinary histories of the agents involved.
Secret Service investigators are in Colombia interviewing witnesses.
In a letter to Secret Service Director Mark Sullivan, Issa and Representative Elijah Cummings, the committee's top Democrat, said the agents "brought foreign nationals in contact with sensitive security information." A potential security breach has been among the concerns raised by members of Congress.
King said Sullivan took employment action against "the three people he believes the case was clearest against." The lawmaker said the agency was "reasonably confident" that drug use was not an issue with the three agents who have been forced out. But he said Secret Service investigators would continue to look into whether drugs played a role in the incident as it continues talking to the other eight agents involved.
Hotel workers told Secret Service investigators they found no drugs or drug paraphernalia in the rooms where the agents stayed, according to a person familiar with the investigation. The person was not authorised to discuss the probe publicly and spoke only on condition of anonymity.