CARTAGENA, Colombia (AFP) — A sex scandal involving Secret Service agents on US President Barack Obama’s trip to Colombia appeared to grow Sunday after visiting American soldiers were also linked to the use of prostitutes.

Eleven members of the service, known for their robust handling of security for senior members of the US Government, were suspended and sent home following allegations of misconduct in the resort city of Cartagena.

Five US military personnel are also being investigated for behaviour said to have taken place at the same hotel where the Secret Service staff were staying, and they have been taken off duty and confined to barracks.

Obama arrived late Friday in the Caribbean port of Cartagena, under security lockdown for the Summit of the Americas, but the allegations against the Secret Service and military completely overshadowed the gathering of regional leaders.

The misconduct claims were made on Thursday against the Secret Service personnel, who included both special agents and uniformed division officers, though none of them was assigned to Obama’s personal security detail.

Secret Service Assistant Director Paul Morrissey said “the nature of the allegations, coupled with a zero-tolerance policy on personal misconduct”, led to the “decisive action to relieve these individuals of their assignment”.

Having been sent back to the United States, the personnel involved were taken to the service’s Washington headquarters for interviews on Saturday as part of the agency’s internal affairs division’s investigation.

“As a result, all 11 employees have been placed on administrative leave. This is standard procedure and allows us the opportunity to conduct a full, thorough and fair investigation into the allegations,” Morrissey said.

The Washington Post, quoting Jon Adler, president of the Federal Law Enforcement Officers Association, reported that at least one agent had been involved with prostitutes in Cartagena.

Ronald Kessler, a former Post reporter and author of a book on the Secret Service, told CNN the scandal erupted when one of the agents “did not pay one of the prostitutes, and she complained to the police”.

Meanwhile, Republican Representative Peter King, who chairs the House Homeland Security Committee, told The New York Times that the 11 agents were suspected of bringing women back to their rooms.

While prostitution is legal in designated areas in Colombia, such behaviour would violate agency rules of conduct, in part because it could expose the agents to blackmail, facilitate espionage and help an enemy get inside a security perimeter, said King, according to The Times.