Ontario's Special Investigations Unit has determined police had "nothing to do" with the death of a man who had ingested drugs at a music festival held in Toronto this summer.

The Veld music festival was held during the first weekend of August at Toronto's Downsview Park.

The SIU says a 22-year-old man who was at the festival on Aug. 3 went into medical distress on Aug. 4.

After the man was helped to an emergency medical area, he began to convulse and flail "violently," and his movements prevented paramedics from treating him, the SIU says. 

A police officer handcuffed the man's hands to a stretcher so he could be treated. The SIU says one of his hands was later freed so that medication could be given to him.

The man was subsequently rushed to hospital and went into cardiac arrest en route. His remaining handcuffs were removed and the ambulance stopped. But he could not be revived by paramedics or hospital staff.

The SIU has found that the evidence indicates the man died "from a combination of myocardial infarction and renal failure brought about by the ingestion of a combination of illicit drugs."

The SIU has closed its file on the matter. The police watchdog investigates all incidents involving police in which members of the public have been seriously hurt or killed, or when allegations of sexual assault have been raised.

Toronto police have said that two people died and more than a dozen others fell ill after ingesting pills at the festival. Authorities have been investigating as to what the pills are and investigators have made appeals for members of the public to come forward with information about the drugs.