Highways England have now closed the M1 after a crash earlier this morning.
The motorway is shut southbound between Northampton and Milton Keynes from junctions 15 to 14.
There are diversions in place with drivers asked to follow the hollow circle symbol via the A508/A5/A509.
Two crashes were reported on the M1 this morning which had initially caused the delays.
Highways England have since taken the decision to shut the motorway while recovery is carried out.
UPDATE: Two lanes have been closed northbound between junctions 14 and 15.