Cory Monteith died from a lethal combination of heroin and alcohol.
The Glee star, 31, was found dead in his room in the Fairmont Pacific Rim hotel in Vancouver, Canada, by staff after he missed his checkout time on Saturday (13 July), and his autopsy results reportedly show that he died from "mixed drug toxicity".
The British Columbia Coroners Service claims that toxicological analysis has shown that the actor, who left rehab in April after voluntarily checking in there for a month, died from "mixed drug toxicity, involving heroin and alcohol."
The Canadian star, who first sought treatment in rehab when he was 19, was very open about his struggles with addiction in the past.
According to gossip website TMZ.com his final cause of death might not be known for a few more weeks.
Police have refused to say whether drug paraphernalia had been found in his room but are not looking for anyone else in connection with his death.
It was previously claimed that the Glee cast spent a lot of time keeping Cory sober in Los Angeles but when he returned to Vancouver "alcohol and drugs were always involved" and his drive to stay clean withered.
Apparently, Cory also attended several Alcoholics Anonymous (AA) meetings in the days before his death. A source close to him told RadarOnline.com: "Cory went to AA meetings when he got to Vancouver with some friends of his and mine. They have attended AA meetings in the past together. Vancouver is a great place to keep grounded when you are in the spotlight and trying to be sober. Being grounded is the key to sobriety and that's what Vancouver can offer Cory. It is casual and he calls it home and he has friends here who have known him for a long time. Cory also works helping kids stay out of these drug problems that are so apparent in the Downtown Eastside."