Ontario Provincial Police closed a stretch of Highway 401 after an unidentified man was struck and killed in an apparent hit-and-run on Sunday morning.

Police shut down the westbound lanes of the highway between Mill Street and Highway 115/35 connection, near Newcastle, Ont., after they found the body while responding to a report of a deer being hit.

Const. Dave Woodford said the pedestrian, who had no ID on him but is believed to be in his early 20s, was hit shortly before 6 a.m.

Evidence indicates that the driver, who failed to remain at the scene, was in a tractor-trailer when the victim was struck, Woodford said.

Police are now looking for a Volvo rig. Woodford said the vehicle will likely have extensive damage to its front end and could be leaking antifreeze.

The OPP are also looking for a man who called police around the time of the incident and reported an animal being hit in the same location.

"We think he may have seen something that looked like a deer," Woodford said.

"We had officers respond, and found it wasn't a deer."

Police said it's not clear why the victim was walking on the highway. OPP criminal investigation, traffic investigation, and identity officers remained on the scene Sunday afternoon.

Anyone with information about the incident can call Const. Dave Woodford at 416-553-5471.