TORONTO - Ontario's police watchdog has closed its investigation into the death of a 22-year-old man who was handcuffed to a stretcher while suffering from convulsions.

The Special Investigations Unit says the man's death last month had nothing to do with police actions, but was instead due to "myocardial infarction and renal failure brought about by the ingestion of a combination of illicit drugs."

The SIU says the man went into medical distress on Aug. 4, a day after attending the VELD music festival in Toronto.

They say he was "flailing violently," which prevented paramedics from treating him, so an officer handcuffed him to the side rails of a stretcher.

The right handcuff was later removed so he could get an IV. The left was also taken off after he went into cardiac arrest in the ambulance.

The SIU says he couldn't be revived.