Philip Seymour Hoffman was found dead at his New York City apartment on Sunday (Feb 2nd), with a syringe still in his arm. 

Police suspect the 46 year-old died as a result of a drug overdose, and a post-mortem examination is being conducted today (Feb 3rd), but the medical staff are almost certain what killed him.

"We still think it's going to be an overdose," said one source.

Police sources have also said that 5 empty bags and 65 full bags of heroin were removed from the Oscar-winning actor's home by the authorities, (via The Telegraph).

Each bag had the text "Ace of Spades" or "Ace of Hearts" printed across it, these are brand names drug dealers use for heroin. 

According to the Associated Press, Police are now trying to determine if the drug was mixed with anything else, making it a lethal dose. 

They are currently investigating if Hoffman injected himself with the same lethal batch of drug that has caused more than 100 deaths in the neighboring states in recent weeks. 

These batches of Heroin have been mixed with fentanyl, a synthetic morphine substitute roughly 100 times more powerful than morphine, to help ease the pain of cancer patients. 

"The direction of the investigation is going to depend, in large part, on the findings of the medical examiner and the findings of the lab tests," chief police spokesman Stephen Davis said.

Read here of the film projects Hoffman was involved in before his sudden death

While searching the apartment, authorities discovered syringes, some unused, different types of prescription drugs and a charred spoon which is what Hoffman likely used to reach his last high. 

Hoffman, who won an Academy-Award for Best Actor in 2006 for playing the title role in 'Capote', was found by David Bar Katz, a screenwriter and close friend, and his own assistant Isabella Wing-Davey, when visiting his Manhattan apartment at 35 Bethune St. in the West Village.

Philip Seymour Hoffman
Police arriving at Hoffman's NYC apartment