Stratford Police Service say speed and not wearing a seatbelt were likely factors in a vehicle rollover that sent two people to the hospital.
Emergency services responded to a single-vehicle collision north of St. Marys on Tuesday afternoon around 3 p.m.
Police say the occupants were ejected from the car, a 2013 red Chevrolet Cruze.
One, a 24-year-old from Woodslee, was airlifted to hospital with life-threatening injuries. The other, a 19-year-old from Thamesford was taken to St Marys, and later transferred to London with serious injuries.
Police closed down Perth Road 130 from Line 15 to Line 16 for several hours to investigate. It was reopened around 8 p.m.
Based on witness statements, police say the involved vehicle tried to pass another vehicle and was forced back into its own lane due to oncoming traffic, veering off the road and rolling several times.
Perth County OPP allegedly received a complaint about the car roughly half an hour before the crash, for speeding along Hwy 23 near Mitchell.
Anyone else who may have witnessed the vehicle prior to the crash is asked to reach out to Stratford Police constable Nicholas Teahen at nteahen@stratfordpolice.com.