Ontario's police watchdog says it is investigating after a car that being chased by Ottawa police Wednesday evening flipped over, causing one of the passengers to become seriously injured.

The Special Investigations Unit (SIU) said in a news release issued Thursday that police officers conducting a radar blitz on Hunt Club Road stopped a vehicle around 6:30 p.m. they said had been speeding.

The vehicle, a black sedan, stopped briefly, but then fled the scene. Ottawa police then followed the vehicle. 

The vehicle flipped over when it approached the intersection of Pike Street and Maple Park Private and landed upside down in a someone's backyard. 

The SIU said the driver and one of the passengers fled the scene on foot. A third passenger, a 16-year-old boy, was taken to hospital with a serious injury.

​The SIU investigates when incidents involving police and civilians result in serious injury, death or allegations of sexual assault.

Two investigators and one forensic investigator have been assigned to the case. 

The police watchdog is urging anyone with information about the chase to contact the lead investigator at 1-800-787-8529. Anyone with video footage of the incident is also asked to upload it to the SIU website.