The incident is at Rio Recycling in Stanford Road, Orsett.
On arrival the officer in charge reported that the fire was deep seated withing the pile of wood. Heavy plant machinery has been used to create firebreaks and firefighters are using hose reel jets to contain and control the fire while a controlled burn takes place.
A two pump relief took over at the site this morning.
This is expected to be a protracted incident.
Update: 1400 hours
Update 12:57 hrs: Crews have confirmed the fire involves 40,000 tonnes of wood chips in a quarry 80 feet deep and 600 feet wide. Surrounding risks are being protected using a water relay as the fire burns under control. ECFRS Control has been in touch with the Met Office for information relating to wind speed and direction and all appliances at the scene have been repositioned. The welfare unit and a five pump relief is due at the scene at 13:00 hrs.
The A1013 has been closed in both directions from the Orsett Cock roundabout to the next roundabout London bound.
Crews expect to remain at the scene for some days. There is no information relating to the cause at this stage.