The province's Special Investigations Unit is probing a two-vehicle collision in Brampton that happened around 3 a.m. Saturday.
The SIU gave an update at the crash site.
Spokesperson Jason Gennaro says the collision happened after a Peel Regional police officer attempted to pull over a vehicle in the Queen Street and Kennedy Road area. The vehicle fled scene and collided with a cargo van in the nearby intersection of Vodden Street and Rutherford Road.
Gennaro says the 26-year-old male driver of the vehicle was taken to hospital with serious injuries. The 26-year-old male passenger was also taken to hospital.
The two men in the cargo van, 61 and 58-years-old were also taken to hospital.
The SIU invoked its mandate about an hour after being called to the scene.
The SIU is an arm's length agency that investigates reports involving police where there has been death, serious injury or allegations of sexual assault.
With files from Heather Goode