A vehicle crossed over from the anticlockwise carriageway onto the clockwise. Highways England Traffic Officers are currently working at the scene alongside the emergency services.
Highways England said: “Delays are likely on the approach to the closure, with additional journey times also expected on diversion routes.
“Please allow extra time for your journey if travelling in the area or consider alternative routes.”
Essex Police, Essex Fire Service and East of England Ambulance are on the scene.
More to follow…