Hospital chiefs have declared a major incident after the coach overturned at the bottom of an embankment close to Junction 3 of the motorway
Three of them suffered “serious” injuries in the collision and have been rushed to hospital, it has been confirmed.
Police, fire and ambulance crews are at the scene, with the anti-clockwise slip road at junction 3 closed.
Highways officials warned that queues of more than seven miles had built up in the aftermath of the crash, which happened at around 4pm close to the Dartford Crossing.
It could take until nearly midnight for the road to fully reopen, with drivers currently experiencing delays of around 90 minutes.
A nearby hospital confirmed that it has declared a major incident, and firefighters used specialist cutting gear to free two passengers.