The motorway has now fully reopened between Bury and Ramsbottom.
Officers have told us that in the early hours of this morning a car collided with the body of a woman on the Northbound side of the carriageway.
The closure between junction 2 at Bury and junction 1 for Ramsbottom was put in place at around 2am this morning and has now been lifted.
Investigation work has been completed and police are now continuing to try and work out what happened.
It is not clear where the woman was dead or alive when the car collided with her.