UPDATE | OPP were attempting to stop vehicle in St. Catharines crash

There are more details about the single vehicle crash in St. Catharines that closed the area of Fourth Avenue and Highway 406 for about nine hours.

The Special Investigations Unit says an OPP officer was conducting radar enforcement on the eastbound QEW Saturday morning when he attempted to stop "a vehicle of interest."

Instead of stopping, the vehicle turned onto Highway 406 and continued onto  Fourth Avenue where  it crashed into a retainer wall.

Both the 20-year-old male driver and the 21-year-old male passenger were airlifted to hospital.

One was taken to Hamilton General. The other was taken to St. Mike's in Toronto.

No word on their condition.

The SIU has assigned  two forensic investigators and one collision reconstructionist  to the case.