Caledon OPP are investigating a serious four-vehicle collision that took place last week near Old School Road on Highway 10.
Three commercial vehicles and a passenger vehicle were involved.
The driver of the passenger vehicle sustained serious and life-threatening injuries and was transported to a Toronto-area trauma centre.
The investigation is ongoing.
Anyone who may have witnessed the collision or has dashcam footage is asked to contact Caledon OPP at 905-584-2241 or 1-888-310-1122.