Traffic between Junction 27 at Standish and Junction 28 at Leyland were affected.
The motorway has re-opened in both directions after reports of a man falling from a bridge across the carriageway.
Traffic has now returned to normal after the carriageway was re-opened an hour ago.
An air ambulance left the scene around 10:40.
It is unclear what the mans injuries are at present.At the time of the incident Preston Police posted this on Facebook:
"We are currently at the scene of an incident on the M6, after a man is thought to have come off a bridge close to junction 28 on the northbound side. We will shortly be putting a closure in place between junctions 28 and 29. We would urge motorists to avoid the area if possible and find alternative routes. We will update when we can"