The southbound lanes of Highway 400 have reopened to traffic after a dangling road sign was removed, but police are still looking for the dump truck driver who hit it.

The highway was completely blocked off at King Roadfrom approximately 5 a.m. to 9:30 a.m., with all three lanes of the highway being diverted.

At 9:30, police let some cars through in the left lane, and traffic returned to normal by 10 a.m.

Road crews removed the sign at Teston Road, which will be replaced at another time.

Early morning traffic was already backed up for kilometres by 6 a.m. Thursday morning, with some cars reversing along the on-ramps to avoid the situation.

Witnesses told Ontario Provincial Police that the sign's support structure was struck by a dump truck with its box lifted at approximately 4 a.m. According to witnesses, the truck pulled over for a while, then left the scene.

OPP are hoping more witnesses will come forward to help identify the truck and its driver.