The A12 has been closed in both directions this evening following a serious crash invovling six vehicles. 

An air ambulance has been called to the scene and all emergency services are responding to the incident. 

The collision happened on the northbound carriageway between junctions 19 (Boreham) and 20 (Hatfield Peverel). 

Essex Police said in a statement: "We are on the scene of a collision on the northbound A12 close to junction 19 at Boreham.

"The main carriageway has been closed whilst emergency services respond to the incident.

"We will provide an update as soon as we practically can."

It is understood the southbound carriageway has been closed to allow the air ambulance to land at the scene. 

Queues of more than three miles have been reported on both sides of the road. 

Drivers are urged to avoid the area.

An Essex Fire Service spokesman said: "Firefighters are in attendance at road traffic collision on the northbound A12.

"Crews from Witham, Great Baddow and Chelmsford were called to Junction 19, between Boreham and Hatfield Peverel, today at 4.29pm.

"The collision involves six vehicles and one person is trapped.

"Police are also at the scene and the carriageway has been closed while emergency services respond to the incident.

"We will provide an update as soon as we can."

Update 7pm

Southbound traffic has now been released and all lanes have reopened.

Delays on that side are now easing. 

The northbound carriageway remains closed.