Essex Police, Essex Fire and Rescue and Highways England are currently at the scene dealing with the incident, which occurred at 7.29am today (Wednesday).
Motorists are advised to allow extra time for their journey as there are long delays in the area. Northbound traffic is being diverted up and over the junction at junction 17.
The southbound carriageway was reopened at 2:30pm, however the northbound carriageway will remain closed until later this evening as the road surface requires significant repairs after it was damaged as a result of the lorry fire.
The repair will be carried out as soon as recovery of the lorry completed and debris has been cleared. The northbound A12 will fully reopen as soon as it is safe to do so.
Highway England provides live traffic information via its website, local and national radio travel bulletins, electronic road signs and mobile platforms, such as the iPhone.
Members of the public should contact the Highways England customer contact centre on 0300 123 5000.
Journalists should contact the Highways England press office on 0844 693 1448 and use the menu to speak to the most appropriate press officer.