A major motorway through Northamptonshire has been closed in both directions following a collision.
The closure has left traffic trapped in both directions between junction 15 for the A508 and junction 14 for the A509.
All traffic is currently being held while police and the fire and rescue service investigate an "unknown chemical substance" according to the AA.
Severe delays of 25 minutes and more are being felt on the M1 southbound. There are queues on at the slip road for junction 16 on the southbound side.