Commuters were facing major traffic delays in Preston on Thursday evening.
Motorists reported tailbacks in Avenham as well as on Ringway, describing the jams as a “traffic nightmare”.
Police said there had been a two-car collision at Primrose Hill off London Road at about 5pm, causing damage to the vehicles.
However, they said that may not have been responsible for the jams.
They said no other accidents had been reported in the area.
One person said it had taken 35 minutes to travel from Corporation Street to the junction of Ringway and North Road, with gridlock heading out of Preston towards London Road.