Traffic was held until 8.50am between J28 (Leyland) and J27 (Standish) after an accident on the southbound carriageway, but has now been released.
All lanes have reopened but there are delays with a travel time of around 60 minutes between J29 (M65, Lostock Hall) and Standish (J27).
Highways say the crash happened in lanes two and three near Charnock Richard Services.
There are no details on casualties at this stage, but Lancashire Police and North West Ambulance Service have been approached for updates.