Ontario's Special Investigations Unit (SIU) is probing a serious crash involving a motorcycle being pursued by the Sarnia Police Service (SPS).
It happened just before 5:20 p.m. Thursday on London Road between Montcalm Avenue and Elizabeth Street.
The roadway was closed until around 12:40 a.m. Friday.
The SIU said preliminary information suggests an officer in a marked pickup truck attempted to pull over the motorcyclist, but the motorcyclist fled and collided with another vehicle.
The 31-year-old male motorcyclist was taken to hospital with serious injuries, and no other serious injuries were reported.
Depending on the outcome of the investigation, further details could be made available at a later date.
