A man is dead after being struck by a truck on Highway 401 in Whitby overnight.

On Wednesday, Ontario Provincial Police responded to a collision involving a pedestrian and transport truck on the westbound lanes of Highway 401 at Thickson Road, at around 11:30 p.m.

A 34-year-old man from Toronto was pronounced dead at the scene, police said.

The cause of the collision is unknown.

The highway was closed but reopened early Thursday morning.