The cause of Oscar-winning actor Philip Seymour Hoffman's death remained a mystery Wednesday after an autopsy proved inconclusive, officials said.
The New York City medical examiner's office said any ruling on the cause would have to wait for toxicology tests. It is unknown how long that will take, spokeswoman Julie Bolcer said.
"Our examination has been concluded, but the results are inconclusive," Bolcer said. "We are awaiting results and additional studies."
Police have said Hoffman, 46, appeared to die from a drug overdose. He was found dead Sunday with a needle in his arm in the bathroom of his West Village apartment, police said.
At least 50 packets, some containing heroin, were found in the apartment along with unused syringes and a charred spoon. Prescription medications, including a drug used to treat heroin addiction, a blood pressure medication and a muscle relaxant, also were found at the scene, authorities said.
Hoffman had acknowledged abusing drugs and told CBS' "60 Minutes" in 2006 that he had used "anything I could get my hands on" before getting sober at age 22. In interviews last year, Hoffman said he had relapsed, developed a heroin problem and gone into rehabilitation for a time.
On Tuesday night, four people were arrested on suspicion of drug offenses, but police would not say whether they were connected to the death.
But local news media, citing unidentified police sources, reported that the arrests came after raids based on information gathered from the Hoffman investigation and that authorities were looking at whether the four could have been drug suppliers to the actor.
Robert Vineberg, 57, and Thomas Cushman, 48, were 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. All are from New York, police said.
It is unclear under New York law whether any dealer can be charged with homicide in connection with Hoffman's death if it is ruled an accidental overdose.
"It is very difficult to convict a drug dealer for homicide as a result of selling drugs to someone who later dies," said Larry Cunningham, a former prosecutor who serves as associate academic dean and teaches criminal law at St. John's University School of Law in New York.
"The state would have to prove, beyond a reasonable doubt, that the dealer's drugs were, in fact, the ones that caused death and that death was foreseeable," he said. "Second, the state would have to prove that the dealer intentionally, recklessly or negligently gave the drugs to the person. In other words, that the dealer meant for the person to die, knew there was a high risk of death or should have known that death was possible. This is a very difficult standard to prove."