Drivers are advised to take different routes while working on road cleaning.
Resources from National Highways are in place to handle the spill, which is located in lane 2 and covers an area of approximately 1,500 meters of the highway.
National Highways said: “Every effort is being made to effectively handle the spill to prevent any need for emergency resurfacing. The driveways have been closed to allow this work to be carried out safely at the scene.
“There are currently long delays of at least 90 minutes than usual flight times between the M25 at J30 (Lakeside, Essex) and Mashhad. Customers planning to travel from Essex to Kent via Dartford Crossing are advised to allow plenty of additional flight time.
“If this closure affects your planned route, please allow additional flight time. Plan in advance, you may wish to change your itinerary or even delay it.”