US Secret Service agents leave over Cartagena scandal
Three members of the US Secret Service are leaving the agency following the prostitution scandal in Colombia.
Assistant Director Paul Morrissey said one supervisor was sacked, one retired and a more junior employee resigned.
Senior US officials said 20 women were found at the hotel in Cartagena, Colombia, before President Obama went to the Summit of Americas last weekend.
Lie detector tests are being used on the accused as investigations into the scandal continue.
Internal investigators have interviewed witnesses in Cartagena, where a group of agents and military personnel allegedly spent the night with prostitutes at a hotel being used by the American delegation.
Up to 12 members of the US military are also under investigation.
"We demand that all of our employees adhere to the highest professional and ethical standards and are committed to a full review of this matter," Mr Morrissey said in a statement.
He said inquiries were at an early stage, and another eight officers were still being investigated.
They have been placed on administrative leave and their security clearance had been revoked. They were not directly involved with presidential security.
The two supervisors leaving the Secret Service are both said to have more than 20 years experience.
The BBC's Steve Kingstone in Washington says the scandal is still causing huge embarrassment for the service. He adds that the agency's directors will hope this decisive action brings the scandal under control.
Senator Susan Collins said after a briefing by the head of the Secret Service Mark Sullivan that he was "rightly appalled by the agents' actions".
"He ordered all the agents to return to Washington immediately, and all have been interviewed," Ms Collins, the top Republican on the Senate's Homeland Security and Governmental Affairs Committee, said in a statement.
Speaking to reporters on Tuesday, Ms Collins, a Republican who represents Maine in the Senate, also said she had asked Mr Sullivan a number of questions during her phone briefing.
"Who were these women? Could they have been members of groups hostile to the United States? Could they have planted bugs, disabled weapons, or... jeopardised [the] security of the president or our country?"
A Marine Corps spokesman said on Tuesday that among the military service members being investigated were two Marine dog handlers assigned to support the Secret Service.
The White House meanwhile said it had confidence in the director of the Secret Service to investigate the incident, adding that he had addressed the matter quickly.
General Martin Dempsey said the military did not know exactly what had happened in the Colombian city of Cartagena, a colonial city on the country's Caribbean coast and venue for the Summit of the Americas.
"What we do know is that we distracted the issue from what was a very important regional engagement for our president," he said, adding it was an embarrassment for the agency.
Details of what happened on Wednesday night are still coming to light. The group of military and Secret Service agents were partying at Cartagena's Pley Club, which has been described as a high-end strip club in an industrial part of the port city.
Members of the Secret Service paid $60 (£38) each to the club's owners to bring at least two women back to the Hotel Caribe, where they were staying, the Washington Post reports.
The next morning one of the women demanded more money and a dispute ensued.
ABC News has said the agents were bragging about their work for the president, telling their company that evening: "We're here to protect him."