In a statement on Monday, The British Columbia Coroners Service said there was no evidence to suggest 'anything other than a most-tragic accident'.
Police Constable Brian Montague confirmed 'There was evidence in the room that was consistent of a drug overdose' adding that he wouldn't 'go into specifics'.
'Mr. Monteith was alone when he died. He took the heroin when he was alone by himself.'
The 31-year-old actor was found dead in his hotel room on Saturday night, with reports at the time suggesting police believed drugs not to have been involved.
Montague addressed surprise at the findings in light of the initial report, explaining 'It was the opinion of the investigators that it was a drug overdose, but we didn’t want to speculate,' he said. 'The last thing we would want to do is speculate a drug overdose and then have that not be the case.'
Confirming the circumstances of the tragic death, a Vancouver Police Department spokesperson said 'Mr. Monteith was alone when he died. He took the heroin when he was alone by himself.'
Since news of the death of the actor broke there has been an outpouring of grief from friends and fans the world over.
Cory's girlfriend, actress Lea Michele, thanked fans for their support and love in a statement released on Monday that read 'Lea is deeply grateful for all the love and support she’s received from family, friends, and fans. Since Cory’s passing, Lea has been grieving alongside his family and making appropriate arrangements with them'
'They are supporting each other as they endure this profound loss together. We continue to ask the media to respect the privacy of Lea and Cory’s family.'
Police confirmed that Cory's family are aware of all circumstances surrounding his death.