The agency announced Wednesday that three agents are leaving the service, even as separate government investigations were under way.
The Secret Service did not identify the three agents or eight others 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.
The prostitution scandal 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.
"These are the first steps," said Rep. Pete King, chairman of the House Homeland Security Committee, which oversees the Secret Service. King said the agency's director, Mark Sullivan, took action against "the three people he believes the case was clearest against." But King warned: "It's certainly not over."
King said the agent set to be fired would sue.
The scandal erupted last week after 11 Secret Service agents were sent home from the city of Cartagena 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.
A White House official said Wednesday night that Obama had not spoken directly to Sullivan since the incident. Obama's senior aides are in close contact with Sullivan and the agency's leadership, said the official, who requested anonymity because they were not authorized to speak publicly.
In Washington and Colombia, separate U.S. government investigations were under way. The House Committee on Oversight and Government Reform, led by Rep. Darrell Issa, 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 Sullivan, Issa and Rep. Elijah Cummings, the committee's ranking 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.
The incident occurred before Obama arrived and was at a different hotel than the one he stayed in.
New details emerged Wednesday. A 24-year-old self-described prostitute told The New York Times that she met an agent at a nightclub in Cartagena and, after a night of drinking, the pair agreed the agent would pay her $800 for sex at the hotel. The next morning, when the hotel's front desk called because the woman hadn't left, the pair argued over the price.
"I tell him, 'Baby, my cash money,'" the woman told the newspaper. She said the two argued after the agent initially offered to pay her about $30 and the situation escalated, eventually ending with Colombian law enforcement involved. She said she was eventually paid about $225.
The episode took a sharp political turn when presumptive Republican presidential nominee Mitt Romney said he would fire the agents involved.
"The right thing to do is to remove people who have violated the public trust and have put their play time and their personal interests ahead of the interests of the nation," Romney said.
When asked, the Romney campaign would not say whether he had been briefed on the situation or was relying upon media reports for details.
At least 10 military personnel who were staying at the same hotel are being investigated for misconduct.
Two U.S. military officials have said they include five Army Green Berets. One of the officials said the group also includes two Navy Explosive Ordinance Disposal technicians, two Marine dog handlers and an Air Force airman. The officials spoke on condition of anonymity because the investigation is still under way.
Secret Service's Office of Professional Responsibility, which handles that agency's internal affairs, is investigating, and the Homeland Security Department's inspector general also has been notified.
Sullivan, who this week has briefed lawmakers behind closed doors, said he has referred to the case to an independent government investigator.
Secret Service investigators have interviewed all of the hotel's maids and cleaning ladies, according to a person familiar with the investigation. The person spoke on the condition of anonymity because they were not authorized to speak publicly about the ongoing probe.
Col. Scott Malcom, a spokesman of U.S. Southern Command, which organized the military team assigned to support the Secret Service's mission in Cartagena, said Wednesday that an Air Force colonel is leading the military investigation and arrived in Colombia with a military lawyer Tuesday morning.
The troops are suspected of violating curfews set by their commanders.
"They were either not in their room or they showed up to their room late while all this was going on, or they were in their room with somebody who shouldn't be there," Malcom said.
The incident is expected to come up next Wednesday, when Homeland Security Secretary Janet Napolitano appears before the Senate Judiciary Committee for a previously scheduled oversight hearing.