Essex police have arrested two lorry drivers on suspicion of dangerous driving following a multiple pile-up on the M25 near Lakeside.
One person was killed and five more including a child were taken to hospital following the crash involving three lorries and five cars.
The collision happened between Junctions 29 and 30 shortly before 12:30pm. A section of the clockwise carriageway has been closed with traffic being diverted off and back on the motorway. The road is expected to be closed until later on Tuesday evening.
One person has been killed and five people including a child have been taken to hospital after a crash on the M25 near Lakeside in Essex.
The crash involving three lorries and five cars happened around 12.30pm and the southbound carriageway is closed.
Two air ambulances have been called a serious crash on the M25 near Lakeside in Essex. The East of England Ambulance service says the crash involves multiple vehicles including lorries.
Drivers are being advised to find alternative routes and avoid junction 30 of the M25.
The M25 anticlockwise is blocked with stationary traffic and long delays between J30 A13 (Lakeside / Tilbury) and J29 A127 (Romford), congestion to J1a A282 / A206 Crossways Boulevard / B3228 (Swanscombe).
A second air ambulance is attending the accident on the clockwise side and there are long delays whilst all traffic is held anticlockwise.
The Highways Agency are warning drivers that the M25 in Essex is closed anti-clockwise between J27 and J25 due to a serious incident involving a number of heavy goods vehicles.
A signed diversion is in operation with all traffic advised to leave the M25 anti-clockwise at J27 and follow the square diversion symbol via the M11, A406 and A10 to rejoin the M25 anti-clockwise at J25.
A second traffic alert has also been issued for motorists travelling along the A12 towards London, to be warned that there is a broken-down abnormal load vehicle close to J21, Witham.
The M25 clockwise blocked in Hertfordshire. There's stationary traffic between J21A A405 (St Albans) and J22 A1081 / B556 (St Albans / The Bell Roundabout / London Colney).
All traffic is being held as the air ambulance attends the scene of the accident that has closed the anticlockwise carriageway.
Three lanes closed and queueing traffic clockwise due to an accident involving a car and a lorry between junction 22 (St Albans / London Colney) and junction 23 (South Mimms). Only one lane is open.
The M25 is blocked clockwise in Essex after a serious accident between junction 27 (M11) and junction 28 (A12) earlier this morning.
Delays between junction 6A (M25) and junction 11 (A505 / Dunstable). One lane closed because of flooding. Average speed 20 mph.
Blocked northbound due to an accident at junction 6 (M25).