Three people have been taken to hospital follwing a five vehicle incident.
It happened today on the A12 southbound between junctions 17 (A130/Howe Green) and 16 (Galleywood) at about 7.30am.
Two fire engines were called to the scene to free one man who was trapped.
Two ambulances, the hazardous area response team (HART), two ambulance officers and Hertfordshire Air Ambulance were also dispatched to the scene.
Steve Brant, ambulance officer for EEAST, said: "In total ambulance crews assessed seven people who had been involved in the incident. Fortunately four of them were discharged on scene.
"One man, believed to be in his 30s, was trapped in his car for about 40 minutes and HART worked alongside the fire and rescue service to help extricate him. He suffered potential neck and abdominal injuries and was taken to Broomfield Hospital by land ambulance.
"Two young boys were also taken to Broomfield by ambulance as a precaution but were not thought to be seriously hurt.
"All of the emergency services worked well together on the scene."
One lane remains closed between J17 (A130/Howe Green) and J16 (Galleywood) after the earlier accident. Traffic is also still queuing back along the Chelmsford bypass to J20 (Hatfield Peverel).