Detectives said they were launching a new investigation into the death of Stuart Lubbock whose body was found in a swimming pool at comedian Michael Barrymore's home.
Mr Lubbock, from Harlow, was found dead at Barrymore's home near the Essex town in March 2001.
A lengthy investigation was carried out by Essex Police but no-one was charged with any offences in relation to Mr Lubbock's death.
Mr Barrymore accepted an official caution for drugs offences following the inquiry. A coroner recorded an open verdict following an inquest in September 2002.
Police said their decision to reinvestigate followed a review of the initial inquiry.
Mr Lubbock had been among a number of people at a party at Mr Barrymore's home. Post mortem tests showed that he had suffered severe internal injuries which suggested sexual assault.
Alcohol plus ecstasy and cocaine were found in his bloodstream. His father Terry, also of Harlow, has mounted a constant campaign for a reinvestigation.
The confirmation from Essex Police that they are reopening the investigation follows a failed attempt by Mr Lubbock's father to launch a private prosecution against Mr Barrymore in February.
He wanted the entertainer to answer allegations of drug misuse, disorderly behaviour and assault. But a district judge blocked the move - following the private hearing at a magistrates court in Southend, Essex - saying there was insufficient evidence.
After that hearing Mr Lubbock's father vowed to continue "to fight for justice". In response to Mr Lubbock's father's failed private prosecution, Mr Barrymore said he also wanted to uncover the truth about what had happened to Mr Lubbock.
