The M25 anti-clockwise between J29 and J28 near Brentwood has been closed since around 12pm today (December 12).
Police and National Highways are at the scene as the incident is being dealt with.
AA Maps has reported that congestion now leads to the Dartford Crossing, with 90-minute delays and five miles of congestion on approach.
“If this closure affects your planned route, please allow extra time for your journey,” a National Highways spokesperson said.
“Plan ahead – you may want to re-route or delay your trip.”
Drivers traveling anticlockwise are being advised to follow the Hollow Square diversion symbol and take the following route:
From the M25 Junction 29 exit slip roundabout, take the first exit onto the A127 towards London and continue along the A127 and bear left at the “Gallows Corner” Junction.
At the roundabout, take the fourth exit onto the A12 towards Harwich.
Follow the A12 and take the exit slip for the M25. At the M25 Junction 28 roundabout, take the first exit to rejoin the M25.
