The province's Special Investigations Unit is probing an apparent hit-and-run north of Toronto after a pedestrian was struck by at least three vehicles, including a police cruiser.

York Regional Police is urging witnesses to come forward and were looking to speak to the driver of a Mercedes SUV that they said had fled the scene of the fatal collision.

An SIU statement suggested it was unclear just how many people had hit the 30-year-old victim, whose name and hometown have not been released. At least two civilian vehicles struck the man before police arrived, the SIU said. Officers were dispatched when people in the latter vehicle called in the incident, said York Regional Police spokesman Constable Blair McQuillan.

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"A [York Regional Police] cruiser responding to the scene also came into contact with the same male on the roadway," said the SIU, which has a mandate to investigate incidents of death or serious injury involving police.

The SIU statement used very different language to describe the collisions, saying the civilian vehicles "struck" the man while the police cruiser "came into contact" with him. Watchdog spokeswoman Jas Brar clarified later that the choice of words should not be taken to indicate differing levels of severity.

Constable McQuillan said he could offer no insight into how the police car struck the victim. He said any such information would have to come from the SIU, which said it was too early in the investigation to discuss specifics.

It is unclear at which point in the series of events the man died; and parallel investigations are underway by both York Regional Police and the SIU. The officers are probing the failure-to-remain allegation and the SIU is looking into the role of police in the incident.

The police said that the man was spotted in Richmond Hill at around 3:30 in the morning. He was found lying on Yonge Street, which in this area is a busy arterial road. Constable McQuillan said that physical evidence left by the initial collision pointed officers to a Mercedes SUV. He said the second vehicle to hit the man was a Honda Fit carrying two people, who stopped after the collision and notified police.

Police were seeking the driver of the SUV as well as any witnesses who may have been in the area. Anyone with information was being urged to call the Collision Unit at 1-866-876-5423 extension 7704 or Crime Stoppers at 1-800-222-TIPS.