Washington, Apr 27 (IANS/EFE): The US Secret Service said Thursday it is investigating allegations that agents frequented a strip club and patronized prostitutes in El Salvador ahead of President Barack Obama's March 2011 visit to the Central American country.

The announcement of the probe followed a report by Seattle's KIRO-TV citing the account of an unnamed US government sub-contractor who spent time with the Secret Service advance team in San Salvador.

The purported eyewitness told KIRO that he accompanied a dozen Secret Service agents and several US military personnel to a San Salvador strip club prior to the president's arrival.

Most of the US government employees were "heavily intoxicated", according to the source, and nearly all of them paid an additional fee to enter the club's VIP room, where they received unspecified sexual favours in exchange for cash.

KIRO subsequently interviewed the owner of the club, who confirmed the source's claims and said the Secret Service agents were at his establishment at least three nights in succession during the week before Obama arrived in San Salvador.

The new allegations come amid continuing fallout from a scandal involving Secret Service agents and military personnel who belonged to the advance team for Obama's recent visit to Cartagena, Colombia for the 6th Summit of the Americas.

Agents brought prostitutes back to their rooms at Cartagena hotels, including the one that housed the US president during his stay.

In testimony Wednesday to a Senate committee, Homeland Security Secretary Janet Napolitano said she thought the episode in Cartagena was an isolated incident.

Learning that what happened in Colombia was part of a pattern "would be a surprise to me", she said.