The coroner attributed the cause of death to three things: damage to the air sacs in his lungs, pneumonia and a hardening of his heart muscle with plaque build-up within the blood vessels.
The former teen heartthrob, 38, who collapsed in front of his mother at her L.A. apartment on March 10, had suffered from flu-like symptoms in the days before his death, the coroner said. He had been caring for his mother, Judy, who's battling breast cancer.
On the day he died, police mentioned an overdose as a possible cause of death, but the coroner now confirms that drugs weren't a factor.
Meanwhile, a California Attorney General investigation revealed last month that Haim had unlawfully obtained 553 pills in the weeks before he died. It was previously announced that an arrest was made of a suspect tied to a criminal prescription drug ring linked to Haim.
Haim, who had battled substance abuse issues for years, was laid to rest in his hometown of Toronto on March 16.