Southbound traffic was stopped for around 20 minutes between junctions 31 (Preston, A59) and 29 (Burnley, Blackburn, M65) after the crash at 6.45am.
All lanes are now open, but Highways are advising that some congestion is expected to remain in the area through rush hour.
Lane four (Of four) was blocked until around 7.40am, when traffic was held whilst the vehicles were removed from the carriageway.
The cars have now been moved to the hard shoulder and held traffic has been released.
Highways said it expects delays until around 8.30am, with congestion from junctions 31 to 29 (Bamber Bridge).
Residual delays of around 10 minutes are also expected on approach to the accident scene, with congestion back to junction 31A (Longridge).
A spokesman for Highways England said: "We have a patrol on scene with this and have moved all the vehicles to the hard shoulder."