The "Glee" star was found dead in a Vancouver hotel room July 13, 20013. He was 31.
Billboard.com quoted the B.C. coroner's report as saying Monteith died of a mixed drug cocktail involving "intravenous heroin use combined with the ingestion of alcohol."
The report also noted investigators on the scene discovered "a spoon with drug residue and a used hypodermic needle, along with two empty champagne bottles and glasses" when they entered Monteith's room after he did not check out of the hotel as scheduled.
Notable deaths of 2014 [PHOTOS]