US - The US Secret Service prostitution scandal involved as many as 20 women, 11 American agents and some military personnel, senior US officials say.

  Senator Susan Collins, briefed by the Secret Service director, said 20 women were found at the US hotel.

  The incidents took place in Cartagena, Colombia, ahead of last weekend's Summit of the Americas.

  On Monday, the head of the US armed forces said the Secret Service and the military had "let the boss down".

  Secret Service Director Mark Sullivan was "rightly appalled by the agents' actions and is pursuing a vigorous internal investigation", Ms Collins said in a statement.