The crash happened in lane four of the northbound carriageway when a silver car collided with the central reservation between junction 29 at Lostock Hall and junction 31 at Preston at around 3.50pm.
Emergency services closed three lanes on the southbound carriageway while they dealt with the incident.
Queues built up on both the M6 and M61 heading towards Preston due to the blockage. The incident also affected traffic on the M55 heading towards the M6.
It is not known at this stage if there have been any casualties.