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, 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.
Cory's girlfriend and co-star Lea Michele, 26, who supported him during his struggles, is "devastated beyond belief" about his death.