Washington, Jan 28 : Sources closely linked to the investigation into Heath Ledger's death say that the actor died of natural causes.
According to TMZ.com, sources "intimately connected" with the investigation into the 'Brokeback Mountain' star's death say the level of toxicity from medication in his system was low enough not to have killed him.
The insiders believe that Heath's heart stopped and he may have died from a heart attack despite being aged just 28.
It has also been claimed that authorities suspect Heath was dead for about three hours before he was found in the bedroom of his New York apartment on Jan 22.
They do not believe the housekeeper who found him heard him snoring at about 1pm.
A fireman reportedly observed rigor mortis in Heath's jaw shortly after arriving at the scene at about 3.30pm.
Authorities are also said to be furious at reports which say that there may have been a "sinister plot" to get rid of illegal drugs from Heath's apartment before police and medics arrived.
Sources said that it would have been "impossible" for a bodyguard sent to the apartment by Heath's close friend Mary-Kate Olsen to have taken anything away without cops noticing.