Traffic is queueing back as far as Marks Tey on the London-bound A12 after a three-vehicle accident this morning.
Police were called shortly before 7.15am to the northbound carriageway at junction 20 after a black Ford Ka, a blue Ford Ka and a grey Volkswagen Passat struck each other.
Fire and ambulance crews are both at the scene.
Firefighters using specialist equipment are helping to free one casualty, and at 8.15am the incident commander reported steady progress in rescue operations.
Injuries do not look to be serious at this stage.
All lanes have been reopened between Hatfield Peverel and the Boreham Interchange.
First Bus service has tweeted that their number 70 service is subject to delays.