A crash on the A59 has closed the road as emergency services work to clear the wreckage.
Two cars are understood to have been involved and two people are thought to have seriou injuries.
The bridge near Bank Hall at Tarleton has been shut since shortly after 6pm on Saturday (15 April).
Long delays are being experienced near where the bridge crosses the Leeds-Liverpool canal.
A full closure is in place between the Liverpool Road junction with Carr House Lane and Coe Lane junction of Bank Bridge.
A spokesman for South Ribble Police said: “Please avoid the area and find alternative routes if able.
“We are dealing with this incident as quickly and efficiently as we can and will keep you updated when any changes.”