A crash involving an overturned tanker on the A120 is causing congestion and delays for drivers.
Four crews of firefighters were called to the scene of the accident, near the westbound junction at Dunmow, shortly before 6am.
A white Renault tanker has been overturned in the accident, which also involved a white Ford van, and the driver was trapped inside.
The contents of the tanker, believed to be farm oil, are not hazardous.
Fire crews freed the tanker driver and paramedics treated four casualties.
The 29-year-old male van driver suffered serious injuries, including a possible fractured pelvis, and was taken to the trauma centre at Addenbrookes Hospital.
The male tanker driver was taken to Broomfield Hospital suffering neck injuries, and a further man was taken to Addenbrookes with minor injuries.
A fourth person was assessed at the scene for minor injuries but did not require hospital treatment.
An Essex Police spokesman said: "The A120 has been closed in both directions whilst emergency services are at the scene and the vehicles are recovered.
"Diversions are in place on the old A120. The road could be closed for at least a further two hours.
"Motorists are advised to seek alternative routes where possible."