It happened on the eastbound carriageway between junction 24 at Huddersfield and junction 25 at Brighouse.
All traffic was held as police and ambulance attended the scene.
Traffic has now been released but is moving slowly past the scene of the crash, with delays of about six minutes.
Highways England reported the crash at 2.37pm and said: "There is a traffic collision with multiple lanes closed.
"Traffic is currently passing scene but very slowly."