GUELPH -- A motorcyclist is dead after a crash on Highway 401 near Guelph.

The collision happened Thursday around 3 p.m. near the Highway 6 overpass.

Ontario Provincial Police say the victim is a 57-year-old Oakville man, who was pronounced dead on the scene.

OPP Sgt. Kerry Schmidt said witnesses reported the motorcycle collided with the side of a transport truck.

"As the motorcyclist was merging on to the 401 eastbound, for some reason it lost control and ended up sideswiping a transport truck that was already in the eastbound right lane," Schmidt said. "The motorcycle got tangled up with the side of the trailer and ended up on the right shoulder of the highway underneath the bridge."

No other vehicles were involved. The driver of the transport truck was uninjured.

“The roads are dry. The sky is clear. The conditions are excellent. I don’t know why the motorcyclist lost control,” Schmidt said.

“Right now, we don’t know what was happening as far as what caused him to merge and drift into the path of that eastbound transport truck.”

All eastbound lanes between Hwy. 6 North and Hwy. 6 South were closed for the investigation, with police redirecting traffic. One lane reopened around 6 p.m. By 8 p.m., all lanes had reopened.

The investigation into the collision is ongoing.

Anyone with information or who witnessed the collision is asked to call Cambridge OPP.