Heath Ledger could have died of natural causes and not a drug overdose

Tragic Heath Ledger could have died of natural causes and not a drug overdose, it was reported last night.

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 say Heath's heart stopped and he may have died from a heart attack despite being aged just 28, according to website TMZ.com.

It has also been also claimed authorities suspect Heath was dead for about three hours before he was found in the bedroom of his New York apartment.

They do not believe the housekeeper who found him heard him snoring at about 1pm, TMZ.com says.

A fireman reportedly observed rigor mortis in Heath's jaw shortly after arriving at the scene at about 3.30pm.

Authorities are understood to be furious at reports there may have been a "sinister plot" to remove illegal drugs from Heath's apartment before police and medics arrived.

Sources told TMZ.com 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.

They say officers were there the entire time the bodyguard was present.

By Iain Burchell, Jan 27 2008 © Copyright 2008 - Showbiz Spy