By CHARLIE SAVAGE and ERIC SCHMITT

WASHINGTON — The United States Secret Service placed 11 employees on leave on Saturday as the agency’s internal watchdog opened an investigation into accusations of misconduct involving prostitution in Cartagena, Colombia, where President Obama arrived on Friday for a summit meeting.

In addition, five United States military service members who were working with the Secret Service unit have been confined to quarters and are facing an investigation because they violated a curfew and might “have been involved in inappropriate conduct” in the same hotel as the agents, the military said.

The Secret Service employees, including both agents and officers, had been sent to Colombia to provide support to teams preparing security measures ahead of the president’s arrival. On Friday, the Secret Service abruptly replaced the entire unit.

Details about the episode, which took place on Wednesday night and involved at least two Secret Service supervisors, were coming into focus on Saturday night, though there were still some conflicting details in accounts of what had happened. Officials emphasized that the investigation was still in its early stages.

But in a phone interview, Representative Peter T. King, the New York Republican who is chairman of the House Homeland Security Committee, which oversees the Secret Service, said that he was told in a briefing that the 11 agents and officers were suspected of bringing women back to their rooms.

While prostitution is legal in designated areas in Colombia, such behavior would violate agency rules of conduct, in part because it could expose the agents to blackmail or facilitate espionage, help an enemy get inside a security perimeter and otherwise distract agents when they are supposed to be focused on protecting the president, he said.

The violation came to light, Mr. King said, because under the hotel’s policy, guests of people staying there must leave their identification at the front desk and leave by 7 a.m. On Thursday morning, he said, a hotel manager realized that one of the women had not left and went to the agent’s room to ask her to leave.

The agent is said to have not let the manager in, whereupon a Colombian police officer went to the room. Inside, the woman complained that the agent had not paid her. Eventually the agent did pay her, and she is said to have left without further incident, Mr. King said.

While no law was broken, the Colombian police sent a report to the American embassy recounting the incident.

The embassy and the Secret Service field office in Miami, which supervised the unit in Colombia, began to hear reports of the episode at the same time on Thursday, Mr. King said. They began to investigate and discovered that other Secret Service employees had taken women to their rooms as well. Then the entire team was ordered out of the country, and replacements were flown in from Miami and San Juan, Puerto Rico.

Mr. King said that it appeared that the Secret Service had “responded appropriately,” but he was directing his staff to begin an investigation to determine a precise timeline of what happened, whether it was an aberration, and what procedures were put in place to prevent a recurrence. He said he would decide whether to hold a hearing on the matter based on whether his staff uncovered details that differed from the agency’s public account.

Investigators who interviewed the agents and officers on Saturday were sorting through accounts. In another version of the events, several officials said, the police attention was initially attracted by some kind of argument or altercation — compounded by the language barrier — involving the woman who demanded money from the agent.

A senior United States official who had been briefed on the matter said that it was unclear whether some or all of the other women brought to the hotel were also prostitutes, and, if so, whether the agents and officers knew that ahead of time. At least two of the agents were supervisors, the official added.

“There are people who willingly went to prostitutes and other people who ended up with prostitutes,” the official said. “Either way, it’s just unacceptable.”

The agents and officers were flown out of Colombia on Friday, the same day Mr. Obama arrived for the Summit of the Americas, a meeting of more than 30 leaders.

“The president is obviously aware of the incident, but beyond that, this is a matter that the Secret Service is looking into,” the White House spokesman, Jay Carney, told reporters in Cartagena. The controversy was the subject of the first question to Mr. Carney at a late afternoon briefing on Saturday. He said the matter had not been a distraction for the Obama delegation and added, “I think it has been much more of a distraction for the press.” Mr. Carney said that the White House learned of the matter on Thursday night and that Mr. Obama was told on Friday.

In a statement the assistant director of the Secret Service, Paul S. Morrissey, acknowledged that 11 agency personnel, including both special agents and uniformed division officers, had been recalled from Colombia over allegations of personal misconduct. He said they were interviewed by the agency’s Office of Professional Responsibility on Saturday and have been placed on leave as the investigation continues. The United States Southern Command, which oversees American military matters in Latin America, said the five military service members who were working with the Secret Service had been restricted to their rooms and were “under orders not to have contact with other individuals.” They would return to the United States at the end of the summit, it said, and are facing a military investigation.

Daniel Bongino, a former Secret Service agent with the presidential protection division who left the agency in May, said that while agent misconduct occasionally occurs, in his experience most agents who are on assignment but off duty lead a “monkish” existence focused on working out, eating and sleeping.