WASHINGTON - A top lawmaker briefed on the investigation into a Secret Service prostitution scandal said that more firings could be imminent following the ouster of three agency employees.

"I wouldn't be surprised if you saw more dismissals and more being forced out sooner rather than later," Rep. Peter King (R., N.Y.) said Thursday. King is being updated on the investigation by Secret Service Director Mark Sullivan.

"You may see a few more today or tomorrow," King added.

The Secret Service has moved quickly to quell the scandal that erupted late last week, when at least some of 11 agency employees implicated in the incident brought prostitutes back to their hotel in Cartagena, Colombia, where they were setting up security for a visit by President Obama.

So far, three people involved have lost their jobs. The service said Wednesday that one supervisor was allowed to retire, and another will be fired for cause. A third employee, who was not a supervisor, has resigned.

In Washington and Colombia, separate U.S. government investigations are under way. The Secret Service has investigators in Colombia, and King said he has assigned four congressional investigators to the probe. The House Committee on Oversight and Government Reform, led by Rep. Darrell Issa (R., Calif.), sought details of the Secret Service investigation, including the disciplinary histories of the agents involved.

In a letter to the Secret Service director, Issa and Rep. Elijah Cummings of Maryland, the committee's senior Democrat, said the agents "brought foreign nationals in contact with sensitive security information." The lawmakers have demanded that Sullivan provide them by May 1 with detailed information about the incident, including a full timeline of the events that unfolded in Colombia and assurances that none of the women involved were under the age of 18.

Senate Majority Leader Harry Reid called the Secret Service employees under investigation "stupid" and said there is not much Congress can do to stop others from making similar choices.

"There is not a bill we can pass to cause people to have common sense," Reid (D., Nev.) said Thursday.

Issa said Thursday he would wait until the Secret Service finished its internal investigation before deciding whether to launch his own committee probe.

While congressional lawmakers pushed for more answers from the Secret Service, the White House, frustrated by the election-year embarrassment, pleaded for patience.

"What I'm not prepared to do is to offer you sort of day-by-day commentary on new revelations or even new actions taken with regards to this investigation while it's still under way," White House spokesman Jay Carney said. "I don't think that's helpful to the process."

Carney said Obama remained confident in the Secret Service chief, though he said the president had not talked with Sullivan since the incident unfolded.