Assistant Chief Coroner Ed Winter declined Friday to identify the drugs. Haim was battling flulike symptoms in the days before his death.
Winter says an autopsy was done Thursday, but his office is awaiting the results of toxicology tests that could take two months before determining a cause of death.
Haim died Wednesday in Burbank after collapsing at his mother's apartment. He had been taking care of his cancer-stricken mother in the recent months. The 38-year-old battled drug addiction for years.
In the 1980s, Corey Haim became a teen pin-up favorite, a baby-faced idol with an infectious grin and a "firecracker" personality.
But as he shot to stardom with a string of hit films including the 1987 vampire smash "The Lost Boys," the promising Toronto-born actor fell into a debilitating battle with drugs and alcohol that he later blamed for ruining his career and destroying his health
As of late he struggled to mount a career comeback in Los Angeles. He recently completed several film projects.