The results of an autopsy on Oscar-winning actor Philip Seymour Hoffman's body were inconclusive, and further tests have been ordered, the New York medical examiner's office said Wednesday.

A spokeswoman told AFP that pathologists had not yet reached a conclusion on the cause and manner of the death of the 46-year-old, whose body was found in his New York home on Sunday.

Police, who suspect a drugs overdose as the cause of death, said Hoffman was found with a needle in his arm, and there were 50 envelopes of heroin, syringes and other pills in the apartment.

But the medical examiner's office is awaiting the results of further tests and gave no time frame for when they might be available other than indicating it might take several more days.

US police investigating Hoffman's death arrested three men and a woman with a large amount of heroin in Lower Manhattan Tuesday.

The three men aged 22, 48 and 57, and the woman, 22, were all detained on drug-related charges, a police spokesman told AFP.

According to US media, police said heroin found in Hoffman's apartment did not contain fentanyl, a powerful additive that has been tied to 22 recent fatal overdoses in Pennsylvania.

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