Southbound lane 3 was closed after the crash near the Services between junctions 8 (A674 Millennium Way, Chorley) and 6 (Horwich) at around 4pm.
Traffic ground to a halt with drivers queuing from Botany Bay to the Services whilst traffic officers attend the scene.
Lancashire Police described it as a "minor injury collision" and said no casualties were taken to hospital.
National Highways said the lane closure was likely to remain in place until around 5.15pm.
All lanes have since reopened.
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