Police in northern Alberta believe a hit-and-run semi was responsible for damaging an overpass on Highway 63.

The damage to the Hospital Street overpass in Fort McMurray compromised its structural integrity, say police.

Both northbound lanes of Highway 63 were re-opened Monday, however one of the lanes needed to be closed until later today for further assessments.

Three of the four lanes over the bridge have been reopened.

Police say they got a call about significant damage to the bridge Monday just before 9 p.m.

They also got reports of concrete chunks falling onto the highway lanes.

The suspect vehicle was described as a semi hauling a larger backhoe on a flatbed trailer.

The backhoe collided with the overpass and looked to have sustained considerable damage.

with files from The Canadian Press