A 69-year-old Burlington man died in hospital hours after his vehicle was crushed by a wheel that flew off of a transport truck on Highway 400 near King Road on Wednesday morning.

Ontario Provincial Police Sgt. Kerry Schmidt said the incident happened at around 9:30 a.m. when a truck travelling southbound about 40 kilometres north of Toronto lost a set of wheels, one of which caromed into the northbound lanes and slammed into the victim's SUV.

After the driver was extricated from the badly damaged vehicle, an air ambulance transported him to a Toronto trauma centre in critical condition. Schmidt confirmed late Wednesday that the man died of his injuries.

RAW: OPP officers move wheels that flew off truck on Hwy. 4001:25

Police said it's not immediately clear how the wheels separated from the vehicle. OPP investigators could be seen photographing the trailer from which the wheels dislodged.

An employee from Transport Leo Labelle, the trucking company that owns the vehicle, told CBC News the truck has been towed for further investigation.

The employee, who didn't want to be identified, says the vehicle was transporting wood from from Val-d'Or, Que., to Bolton, Ont.

The employee added trucks are inspected on a weekly basis and said the one involved in the crash was last inspected on Jan. 22.

The truck driver remained on the scene and was co-operating with the investigators.

At one point the southbound and northbound lanes of Highway 400 were closed between King and Aurora Roads, but the highway has since reopened.

Wheel off transport truck

Here's where the wheels separated from the transport truck. (CBC/Shannon Martin)