Toronto Police responded to reports of a pedestrian struck by a vehicle in the area of ​​St.  Clair and Yonge Street.
A man was found at the scene with life-threatening injuries and rushed to a trauma centre, Toronto paramedics said.
Another patient involved in the incident refused to be taken to hospital, according to paramedics.
Police said the driver fled in his vehicle but was later located and arrested.
The eastbound lanes on St.  Clair to Yonge Street are closed for the investigation.