Police are said to have found 49 bags of heroin and 20 used syringes in Philip Seymour Hoffman's New York apartment, suggesting that the actor had sunk deeply into drug addiction as troubles mounted in his personal life.
Mimi O'Donnell, his long-time partner before a recent split, told investigators that he appeared to be "high" the day before his body was found in his bathroom from an apparent overdose, a needle still stuck in his arm.
And a witness has said that the Oscar-winner looked "very sweaty" and in grim condition during what may have been his final, lethal drug purchase on Saturday evening.
The man told police that he saw Hoffman make a large withdrawal from a cash machine near his home and then hand over the money to two men in an apparent drug deal.
In the months before his death, Hoffman was said by friends to be spending up to $10,000 (pounds 6,000) a month on heroin and the prescription pain-killer Oxycontin - allegedly buying up to 50 bags of the class A drug at a time.
The quantity of heroin littering his Greenwich Village apartment indicate that Mr Hoffman, 46, who admitted taking the drug briefly last year after insisting that he had been "clean" for 23 years, was again using the substance heavily.
Police also recovered a variety of prescription drugs that were not issued in his name from the apartment that he recently rented after moving out of the nearby house where he lived with Ms O'Donnell, his partner of 15 years, and their three children.
The fashion designer, also 46, is the last person known to have talked to Hoffman when the two spoke by telephone at about 10pm on Saturday. She told investigators that he sounded "high" in the conversation and also looked to be under the influence of drugs when they met earlier in the day.
The couple are understood to have split around Christmas. Although Hoffman was working on new film projects, including a sequel to The Hunger Games, there were reports of increasingly erratic behaviour in recent weeks.
At last month's Sundance Film Festival, journalists said that he seemed looked ill and "pasty" and declined initially to attend a scheduled party and give interviews before turning up late.
A picture emerged yesterday of Hoffman drinking and smoking in an Atlanta bar on Jan 30. The photograph, believed to be the last taken before his death, showshim with a woman in a restaurant next door to the Hyatt hotel.
The man who took the photograph said he saw Hoffman making an unusual number of trips to the bathroom.
The actor was found dead on Sunday morning by David Bar Katz, a screenwriter and close friend, and his own assistant Isabella Wing-Davey.
Ms O'Donnell and their children were waiting for him at the time in a playground just a few minutes' walk away.
Several of the bags found in the fourth-floor apartment were marked with Ace of Spades and Ace of Hearts, brand names used by drug dealers for heroin.
Police in New York are investigating whether Hoffman injected himself with a doctored batch of the drug that has been blamed for more than 100 deaths among heroin users in nearby states in recent weeks. The heroin has been mixed with fentanyl, an opiate used to ease pain of cancer patients.
But medical experts also noted that the amount of drugs recovered from his apartment could have proved fatal even if it was not mixed with other substances.
A neighbour said that Hoffman, who won the Oscar for best actor for his portrayal of Truman Capote in the 2005 film about the writer, looked "grey, not good" when she saw him the day before his body was found.
Hoffman said last year that he enrolled in drug rehabilitation after taking heroin for a week and realising that he needed help. He previously admitted a history of heavy drug abuse as a young man but said that he had kicked the habit.
"You get panicked," he said, adding that he feared for his life.