Motorists are advised that the M25 anti-clockwise between Junctions 23 and 21a will remain closed during rush hour following a vehicle fire this afternoon.
A lorry carrying cooking oil and foodstuff overturned and caught fire after spilling its contents onto the carriageway this afternoon.
Emergency services have been at the scene since 3.20pm.
Structures engineers are currently on site assessing damage to the road and overhead gantry. A police investigation is underway.
The road will be reopened as soon as it is safe to do so but the closure is expected to last for several hours, and during rush hour.
The M25 is closed anti-clockwise between Junction 23 (access to the A1(M)) and Junction 21a (access to the M1).
Motorists wishing to use the M25 anti-clockwise need to exit the M25 at Junction 23 and take the A1(M) north, exit at Junction 3 and join the A414 west. Take the A405 south and rejoin the M25 at Junction 21.
Drivers are advised to plan their journeys, allow extra time to travel and avoid the area if possible.