The accident, which saw a vehicle overturning, happened between junction 25 for Waltham Cross and junction 26 for Epping.
Currently, the clockwise stretch of motorway remains closed, with Essex Police and the East of England Ambulance Service still at the scene.
The anti-clockwise carriageway had earlier been closed to allow an Air Ambulance to land close to the scene.
This has since reopened, but there is still several miles of traffic s the busy peak trravel period approaches.
A diversion route has been provided for motorists travelling clockwise on the M25.
This advises them to exit at junction 25, following the A10, North Circular Road and M11 before rejoining at junction 27.
Motorists are also being asked to use alternative routes wherever possible.
Highways England said in an update on its website: “The M25 is closed clockwise between Junction 25 (Enfield) and Junction 27 (M11) due to a collision.
“Essex police are in attendance
“Delays are likely on approach to the closures, with additional journey times also expected on diversion routes.”
This is a breaking story. More to follow…