The road is likely to be closed between Flitwick and Bedford/MK South until around 5pm this evening (Monday).
Police were called at approximately 11.09am today to reports of a collision between two HGVs and a car.
Emergency services, including an air ambulance, are currently at the scene and motorists are advised to seek an alternative route.
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Drivers are being diverted off the motorway at J11a on to the A5 Northbound towards Milton Keynes to rejoin the M1 at J13.
Anyone who has dashcam footage or witnessed the incident is asked to call 101 quoting 155 of 11 March.