Ontario Provincial Police are investigating a dump truck crash that shut down part of Highway 401 for several hours Tuesday morning.

Police were forced to close a section of Canada's busiest highway after a dump truck was travelling with its box raised, and the box struck an overhead traffic sign at Don Mills Road.

Because of the damage to the truck and the sign, police closed Highway 401's eastbound collectors from Leslie Street to the Don Valley Parkway.

The lanes reopened at about 6:50 a.m. after the sign was disassembled and the truck was towed.

No injuries were reported, said Ontario Provincial Police spokesman Sgt. Dave Woodford.