The leader of Calderdale Council has said Elland Bridge will be closed for the forseeable future.
Tim Swift said engineers from the council and the Canal and River Trust, who own the bridge, have been onsite and it is likely extensive repairs will be needed.
“Due to the location of the Bridge, it’s difficult to provide diversion routes, but we are working with our partners to identify a temporary solution,” he added.
“The collapse of the bridge at Elland, and the damage to the A646 in the Upper Valley, means that only essential journeys should be made around these affected areas.
“We need to keep roads clear for emergency services and recovery vehicles.”
West Yorkshire Fire and Rescue Service, structural engineers from Calderdale Council, the gas board, electricity board and emergency engineers were called out after midnight to the bridge as the road surface began to sink.
A West Yorkshire Fire and Rescue spokesman said fire crews dealt with a gas leak at the scene and evacuated the Barge and Barrel pub and nearby apartments as a precaution.
The electrity board then worked to isolate the power and crews were on stand by incase of a fire.
A West Yorkshire Police spokesperson said: “Officers are currently dealing with reports of the road surface sinking on Elland Bridge in Elland.
“As a consequence the road is closed and will likely remain so for the foreseeable future.
“This is an evolving incident, we are asking people to please avoid the area if travelling and not to attend the immediate area to watch.
“Appropriate continued assessments are taking place and, where required, occupants of some properties have been asked to leave as a precautionary measure.”
The bridge is now closed in both directions between the A6025 Park Road junction and the Northgate junction.
First West Yorkshire has said its 537 service towards Halifax will operate via the normal route to Huddersfield Road, Elland, then right (instead of left for Morrisons) to Elland Riorges Link roundabout, then left to Lowfields roundabout, left onto Elland bypass continuing the normal route to Halifax via the Calderdale Way.
Halifax to Huddersfield buses will run their normal route on the Calderdale Way, left on the Lowfields slip road to Lowfields roundabout, right to Elland Riorges Link roundabout, right onto Huddersfield Road, picking up at the normal spot outside Elland Co-op.