The driver of a tractor-trailer has died after police say he, for unknown reasons, drove off of the road on Highway 401 in Oshawa this morning.

The tractor-trailer was spotted in the ditch near the eastbound lanes of the highway in the area of Harmony Road shortly before 5:30 a.m.

OPP Const. Lauren Ball said the driver left the roadway and travelled in the ditch for some distance before hitting a tree.

When emergency crews arrived on scene, the driver was without vital signs and was later pronounced dead.

Police have not released the name or age of the deceased.

“We are still waiting to identify the driver and notify next-of-kin,” Ball said.

Ball added that other injuries were reported.

At this point, the cause of the collision is not known.

Ball said officials will be trying to determine if the man suffered some type of medical episode or died as a result of the collision.

“That will come out as a result of the investigation,” Ball said. “Officers are on scene.”

Two right lanes of the highway were blocked just after the Harmony-Bloor exit for several hours this morning. The roadway fully reopened at around 3 p.m.