A police investigation will no doubt reveal more the details of what exactly happened to Heath Ledger. But representatives of Ledger's family said they'd been told by police that the actor's death was accidental.

The actor was found surrounded by sleeping pills. But NYPD is also saying there was no "obvious sign" of suicide.

Academy Award nominee Heath Ledger, 28, has died of a possible drug overdose involving sleeping pills in New York, police have confirmed.

Ledger was found dead in his bed at his apartment on Broome Street, SoHo, in Manhattan, by his housekeeper.

A police spokesman said the cause of death was unknown, despite the presence of drugs.

"We don't have that [the cause of death] yet. The matter is still under investigation," the spokesman said.

Britain's Daily Mail newspaper claimed the 28-year-old actor began dabbling in drugs after his breakup with fiancee, Michelle Williams.

"Heath totally wanted to be on his own these past few months since he and Michelle split in September," one insider was quoted as saying.

"He adored his daughter Matilda and when Michelle called it quits he missed Matilda so much that he was thrown into a deep, dark depression.

"Heath was living in New York to be close to his daughter. But he hardly ever ventured out any more.

"His close friend and Brokeback co-star, Jake Gyllenhaal has been worried about him for months. And he knew Heath was sinking further into a depression. Jake is Matilda's godfather, and he and Heath had become really close since they did the film Brokeback together.

"Michelle will be devastated by the news because she always hoped ... they could manage to work out their relationship for the sake of their daughter."

Ledger was discovered naked and unconscious by his masseuse and housekeeper when they could not stir him from his bedroom. Sleeping pills were strewn around the bed and there was a bottle next to his body. Bottles of Diazepam and Alprazolam, both anti-anxiety drugs prescribed in his name, were also found in the house, according to law enforcement sources.

According to the family members, Ledger started taking sleeping pills after completing movie I'm Not There, in which he played one of the many incarnations of singer Bob Dylan.

He said late last year he "stressed out a little too much" during the Dylan film and had trouble sleeping while portraying the Joker in the newest Batman flick The Dark Knight. He called the character a "psychopathic, mass-murdering, schizophrenic clown with zero empathy".

"I probably slept an average of two hours a night," Ledger said at that time. "I couldn't stop thinking. My body was exhausted, and my mind was still going."

He said he took two Ambien pills, which only worked for an hour.

"Yes pills were found around the body," a New York Police Department spokesman said.

The medical examiner's office will perform an autopsy tomorrow, spokeswoman Ellen Borakove said.

NYPD Detectives and the medical examiner would conduct a thorough investigation - but Ledger's death is not believed to be suspicious.

"As of right now there does not appear to be any criminality at all," the spokesman said.