Toxicology tests will take between three to four weeks.
This comes after a Tuesday night police raid ended with the arrest of four people in New York, not far from Hoffman's apartment. Police say they recovered 350 bags of heroin.
Robert Vineberg, 57, and Thomas Cushman, 48, were both charged with felony criminal possession of a controlled substance. Vineberg was also charged with criminal use of drug paraphernalia. Max Rosenbloom and Juliana Luchkiw, both 22, were charged with criminal use of drug paraphernalia, criminal use of controlled substance, and unlawful possession of marijuana.
There are reports that a tip led police to the suspected drug dealers who allegedly supplied Hoffman with his heroin. But the heroin recovered during the raids did not include the "Ace of Spades" labels of the drug bags found in Hoffman's apartment.
The 46-year-old Oscar-winning actor was found unconscious on the bathroom floor of his New York City apartment on Sunday. Officials say there was a needle in his arm.
Investigators found syringes, more than 50 bags of heroin and numerous prescription drugs in the apartment. They also discovered buprenorphine, a drug used to treat heroin addiction.
Police said Tuesday that the heroin recovered at Hoffman's apartment has tested negative for the powerful additive, fentanyl. The synthetic morphine has been linked to 22 suspected overdose deaths in western Pennsylvania.
Detectives are reviewing surveillance video to try to piece together Hoffman's activities in the hours leading up to his death. Officials said the actor made six ATM transactions for a total of $1,200 inside a supermarket near his home the day before his death.
At about 8 p.m. Saturday, Hoffman spoke with Mimi O'Donnell, the mother of his three children. That was the last known contact that Hoffman had. When Hoffman didn't show up the next morning to pick up his kids, his friend, David Katz, and another person checked on him and found him dead.
A private funeral is expected to be held Friday for family and close friends. Plans are also underway for a memorial service later this month.
ABC News and The Associated Press contributed to this report.