Highway 40 traffic was jammed Thursday morning after the truck accident. (CBC)Quebec authorities have identified a truck driver who died after his vehicle plunged into the waters of the Deux Montagnes Lake, west of Montreal.

Quebec police said the driver is Sylvain Brunet, 48, of Montreal.

An autopsy will determine the cause of death, police said.

It's not yet clear what caused the accident, but authorities are considering three hypotheses: The driver fell asleep at the wheel; He had a medical emergency; The truck had a mechanical malfunction.

Authorities said Brunet lost control and veered off Highway 40 near the Ile aux Tourtes bridge, outside Vaudreuil-Dorion on Thursday morning.

The vehicle plunged off the bridge, crashed on the embankment, and was partially submerged in the water.

The truck caught on fire because of gas and oil residue.

Emergency workers found Brunet inside the truck cabin. He was an employee of Transport Maritime-Ontario, based in Nova Scotia.

The east bound side of the Transcanada Highway remained partially closed to traffic around the Vaudreuil-Dorion exits, to allow police to process the accident scene.

Transport officials are urging drivers to avoid the highway if possible.