The coroner didn't identify the specific drugs in her system, though a full report is due next week. Her death was also determined to be accidental.
Kelly's publicist said at the time that the actress had "voluntarily" checked herself into rehab just days before her death.
"She was battling the addiction problems that have plagued her these past few years," the rep said at the time.
Kelly faced a series of substance abuse and legal problems -- including drunk driving and domestic violence arrests -- after leaving the hit sitcom in 2006. In June of last year, Los Angeles police arrested Kelly on suspicion of DUI, after she allegedly failed a field sobriety test.