The Special Investigations Unit was called after the 19-year-old driver and her vehicle ended up in a ravine. She suffered a broken arm and broken leg and was transported to hospital.
York Regional Police were conducting radar checks in the area at about 7:30 a.m. when they saw the speeding vehicle.
An officer in a cruiser made a U-turn and followed the vehicle, the SIU said.
The car ended up in the ravine a short time later.
The SIU assigned three investigators, two forensic investigators and a collision reconstructionist to the probe.
Legislation requires the SIU to investigate any time someone is seriously injured during an altercation with police.
Anyone who witnessed the crash is asked to contact the lead investigator at 416-622-2314 or 1-800-787-8529 extension 2314.