The FBI tried for more than a decade to build a case against Michael Jackson over allegations of molesting young boys including having him under surveillance while he was in London, newly-released documents reveal.Details of the extraordinary efforts made by US authorities emerged in a 333-page FBI file made public under the Freedom of Information.An FBI special agent travelled to Manila in the Philippines to interview former workers at the singer's Neverland ranch. Officials believed the man and woman had witnessed him molesting boys when they worked at the ranch from 1988 to 1990.The file states that a legal attache for the US embassy in London was sending back information regarding alleged sexual misconduct by Jackson in England — specifically a phone call to a teenage boy.