The M1 is currently closed southbound between J18 at Daventry and J16 at Northampton due to an accident.
Long delays are currently being reported on the approach, with queues back to before J19 for the M6.
Diversions are in place using the A5, which is also suffering from congestion as a result.
Traffic trapped inside the closure is now being released by officials using a single lane past the scene.
There is also queuing traffic on the northbound side past the scene due to traffic slowing to look at the incident.
It is not known when the road will re-open.