It is not known whether anyone has been injured at this stage, but Lancashire Police and North West Ambulance Service have been approached for further details.
The closure has led to congestion back to junction 5 (Guide / Shadsworth). There are also delays on the A674 Preston Old Road and A6062 Livesey Branch Road on the diversion routes.
Traffic travelling west towards the M6 and M61 was brought off the motorway via the exit slip whilst emergency services work at the scene.
Motorists were told to take a short diversion off the exit ramp before rejoining the motorway at the westbound entry slip road near the Hoghton Arms.
It is leading to queues along the exit and entry ramps, as well as delays for those joining the M65 from Bolton Road (A675) and Chorley Road (A674).
Diversions are in place and traffic is asked to follow the Hollow Square Symbol via Blackburn and Feniscowles, leading to congestion on surrounding roads.