Highways England first reported the "very serious collision" at 9.20pm on Monday,
It happened on the northbound carriageway between junction 39 and junction 40.
An air ambulance was called out to the scene of the crash, as well as paramedics and West Yorkshire Police.
Traffic stuck behind the closure began to be turned around at 11.30pm and all vehicles were released by 1.40am on Tuesday.
A diversion route was put in place and the road remained closed until 6am, as police investigated the crash.
A full statement on the incident is expected to be released by West Yorkshire Police today.