The musician's assistant found him "unresponsive" on his bed, reports TMZ. In a statement released today, the Los Angeles County Department of Medical Examiner-Coroner said Miller's death was accidental.
The 26-year-old - who split with singer Ariana in May - was found in September at his San Fernando Valley home.
The pair had dated for nearly two years and following their split said they would remain "the closest of friends".
According to a toxicology report, Mac Miller was found with his head resting on his knees.
The assistant described him as already being "blue" in the 911 call, according to TMZ.
There was a quarter-inch abrasion on the bridge of his nose, with blood coming out of one nostril.
And an empty bottle of alcohol was found on the nightstand, the report said.
Prescription pills including Xanax and Oxycodone were also found in his home.