The first autopsy performed on Heath Ledger’s body was unable to determine the precise cause of the actor’s death, the medical examiner in New York has revealed.

"The autopsy was inconclusive," New York City Medical Examiner spokeswoman Ellen Borakove was quoted by People as saying. "We have to do further testing including toxicology and tissue testing. Neither cause of death or manner of death has been concluded. We expect additional results in 10 days to two weeks."

Prescription sleeping pills and anti-anxiety pills were found in bottles in Ledger's bedroom and bathroom.

While his death may not be suspected to be a suicide, drugs, not just sleeping pills, more likely than not, also played a part in the tragic death of the 28-year-old actor, who was found unresponsive in his New York apartment Tuesday afternoon.

According to reports, drug packets were found inside the actor's SoHo Apartment, as well as a $20 bill with narcotic residue. TMZ.com reported that the bill was rolled up "in a certain way" with a powdered substance on it, citing NYPD sources. Police are testing the bill and results are expected in the next 24 hours, NYPD Commissioner Ray Kelly said Wednesday at a press conference.

Despite the fact that Ledger was suffering from pneumonia at the time of his death, a prominent forensic pathologist not involved with the investigation ruled it out as a possible cause of death claiming that if it were the case, that would have been evident in Wednesday's initial results, given that it is "readily identifiable at the time of autopsy, because the lungs, instead of being filled with air, are filled with fluid, and we die from pneumonia because we can't breathe."

"I would assume under the circumstances that if he'd die of pneumonia that would be clearly stated, because of concerns from the family," he added.

The actor’s two-year-old daughter, Matilda, and her mother, actress Michelle Williams, who were in Sweden when they received the tragic news, returned to New York on Wednesday.

"Michelle was so quiet ... not saying a word. She was in her own world," a witness who say Williams at the airport was quoted by Us Magazine as saying.

"Everyone feels terrible for her and her child," a Mammoth crew member added. "It's terrible news and saddening for us all."

One of Ledger’s former girlfriends, Australian actress Naomi Watts, who was at Sundance to promote a new film, cancelled all her media appearances.  
Production on Heath's most recent film, the Terri Gilliam-directed “The Imaginarium of Doctor Parnassus,” was shut down.

Warner Bros., who are releasing the next Batman movie with Ledger as the Joker, says, "The studio is stunned and devastated by this tragic news. The entertainment community has lost an enormous talent. Heath was a brilliant actor and an exceptional person. Our hearts go out to his family and friends."