Charges are pending after an early-morning collision somewhere between St. Thomas and Talbotville.
Elgin OPP say they responded to Sunset Drive north of Major Line around 2:30 a.m. on Thursday along with crews from the Southwold Fire Department and St. Thomas Elgin Paramedics.
Officers say a vehicle left the roadway and hit a hydro pole.
The 58-year-old man who was behind the wheel was treated and transported to hospital by paramedics in serious condition.
Investigators say his condition changed to life-threatening once at hospital.
He was the only person in the vehicle. Officers say charges are pending the completion of the investigation.
RELATED: 4 adults, 1 infant hospitalized with minor injuries in fiery St. Thomas crash
Investigators closed Sunset Drive between Major Line and Hwy. 3 until roughly 1 p.m. Thursday.