The A1 is blocked southbound after a vehicle caught fire between Sawtry and Alconbury.
There are long delays as emergency services attend the scene.
A Highways England spokesperson said: “All lanes are currently blocked on the A1(M) southbound between J15 and J14 in Cambridgeshire. A vehicle on the hard shoulder has caught fire. Emergency services are in attendance. We are hoping to have lanes 3 and 4 open very soon.”
The AA have said the vehicle had broken down on the hard shoulder before is caught on fire.
Cambridgeshire Fire and Rescue are at the scene.
Traffic is also queuing in both directions on the A605 at Well Lane near the construction area with increased traffic as motorists attempt to avoid the A1m.
UPDATE: Lanes 3 and 4 have now reopened.
More as we have it...