An autopsy has since been completed and his body was released to his family on Tuesday, with the cause of death being "deferred pending additional tests", a Los Angeles County coroner spokeswoman told the magazine.
Over the weekend Miller's mother shared a photo of her and the rapper attending a baseball game, captioning the photo with a love heart emoji.
Grande has also shared a tribute on Instagram to Miller, posting a candid black and white photo of him.
Miller and Grande split in May after almost two years of dating and the rapper was reported to be struggling following their breakup.
Miller, real name Malcolm McCormick, had spoken about his struggles with drug use and depression on multiple occasions.
In his 2014 mixtape Faces, Miller detailed using cocaine, angel dust and codeine and rapped that "a drug habit like Philip Hoffman will probably put me in a coffin".