The province’s police watchdog is investigating after a three-vehicle crash in the city’s Downsview area Friday morning left six people injured, one critically.

The Special Investigations Unit (SIU) said a Toronto police officer was conducting radar in the area of Wilson Avenue and Keele Street shortly before 11:30 a.m. when a northbound Mercedes-Benz SUV travelling at a high rate of speed was observed.

The officer followed the vehicle and attempted to stop it.

The vehicle later became involved in a collision with two vehicles at the intersection of Keele Street and Sheppard Avenue West.

The SIU said the Mercedes-Benz collided with a Honda travelling west on Sheppard Avenue West and with a Hyundai that was making a left turn from Keele to Sheppard.

It resulted in one of the vehicles rolling onto its roof and catching fire.

The driver of the Mercedes-Benz, a 23-year-old man and a woman from the Honda were transported to hospital with serious injuries.

Four occupants of the Hyundai were also taken to hospital, but their injuries are not considered serious.

The SIU has assigned three investigators, two forensic investigators, and a collision reconstructionist to the incident.

One subject officer and one witness officer have been designated.

“We are cooperating and support the SIU investigation,” said Toronto police Insp. Katherine Stephenson.

The SIU is called in to investigate incidents involving police officers where there has been death, serious injury or allegations of sexual assault.