Despite a completed autopsy, rocker Tom Petty's exact cause of death has yet to be determined.

The autopsy was conducted Tuesday, Los Angeles County coroner spokesman Ed Winter told the Associated Press. While no foul play is suspected, Winter says the coroner investigates all deaths where the deceased hadn't seen a doctor in six months.

Petty, 66, was found unconscious and in cardiac arrest at his Malibu home Sunday. He died at the UCLA Medical Center on Monday evening.

Results of the toxicology screening — to determine whether Petty had any drugs in his system — could take several weeks.

Petty was a longtime smoker. As he told Men's Journal in 2015, he smoked from the time he was 17, though he had gone down to less than a pack a day. 

In June 2010, he was trying to quit, even taking up electric cigarettes, which helped his wife, Dana, quit smoking.

"I've cut way down," he told USA TODAY. "You get vapor and a shot of nicotine, nothing burning."

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Contributing: Maria Puente, The Associated Press