Bridge collapse in US leaves three injured

Three construction workers in the US have been injured after a century-old bridge they were rebuilding collapsed as they walked across it.

Heartstopping footage shows the men working on the North Broad Street Bridge in Ridgeway, Pennsylvania on Thursday afternoon when it suddenly gave way, 6 ABC reports.

One was driving an excavator and the others were walking when they fell.

The bridge was built in 1912 and was recently assessed as being in "satisfactory" safety condition.

Paul Roman, a spokesman for Francis J Palo Inc, which is contracted to repair the bridge, said the company "still doesn't know what happened".

"The bridge just buckled," he said.

One of the men was airlifted to hospital with head injuries, with the other two taken by ambulance suffering a sprained ankle and shock.

"It will probably be a while before we know everything," Mr Roman said.