Weiland passed away in his sleep while on a tour stop in Bloomington, Minnesota, with his band The Wildabouts on December 3.
Weiland was a remarkable vocalist and frontman for influential Seattle grunge band Stone Temple Pilots.
Officials also noted Weiland had a history of cardiovascular disease, asthma and dependence on several substances, according to the report.
"Manner of death is accident", the office said in a brief statement.
After decades struggling with substance abuse, Scott Weiland has reportedly died of an accidental overdose.
Weiland had a long string of drug and alcohol-related arrests and stints in rehab. In later years he also fronted rock supergroup Velvet Revolver, but his true legacy is with STP.
He left behind his wife Jamie Wachtel and two kids Noah, 15, and Lucy, 13, who he had with his first wife Mary Forsberg Weiland. "What they truly lost on December 3rd was hope". The former Velvet Revolver singer was 48.
Former Nirvana bassist Krist Novoselic wrote: "Really sorry to hear about Scott Weiland".
He later returned to the reformed Stone Temple Pilots - but in 2013 they, too, ejected him from the band, claiming he had been "misappropriating" their name to further his solo career.