NEW YORK, N.Y. – Medical examiners were conducting an autopsy Monday on the body of Philip Seymour Hoffman as investigators scrutinized evidence from the scene of the actor’s death, including packets that enforcement officials said were believed to contain heroin.

An autopsy was pending the day after the Academy Award-winning actor was found dead in his apartment in Manhattan’s Greenwich Village. While there was no official ruling yet on what caused the 46-year-old’s death, two law enforcement officials said it was believed to be a drug overdose.

Hoffman was found in a bathroom with a syringe in his arm and with glassine envelopes of what was believed to be heroin, the officials said.

Some of the one-dose packets were stamped with the ace of hearts symbol, and others with the words “Ace of Spades” and that symbol, another law enforcement official said. All the officials spoke on condition of anonymity because they were not authorized to talk about evidence found at the scene.

Stamps are common as a form of drug-world branding, and authorities make note of the ones they encounter. It wasn’t immediately clear whether the ace of hearts and ace of spades stamps could lead investigators to any clues about the source of the items found in Hoffman’s apartment.

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Associated Press writer Tom Hays contributed to this report.