A diesel spill from a lorry's fuel tank has closed the M61 motorway in Lancashire at J9 at Chorley.
Police believe that an object was blown underneath the north-bound lorry, rupturing its fuel tank as it neared the M61 and M6 intersection at Blacow.
The M6 northbound is down to a single lane near J30 (Blacow). Motorists have been advised to expect queues and delays in the area.
The police have said that the motorway road surface will have to be re-laid.
Several cars have been involved in crashes after driving through the diesel spill, but no injuries have been reported.