Three cars and a van were involved in the collision on the M25 clockwise, between Clacket Lane Services and J6 A22 near Godstone. One person has died at the scene.
A spokesperson for National Highways confirmed a casualty caused by the collision.
In an update from 10.05am they said an ambulance was also at the scene.
The spokesperson said: “A multi vehicle collision has occurred on the M25 clockwise, near Godstone. lane 3 has opened.
“Lane 4 (of 4) remains closed. One casualty, ambulance on scene.”
At 11.19am, National Highways: South East posted on Twitter: “All lanes have now reopened on the #M25 clockwise between J5 (#Sevenoaks) and J6 (#Sevenoaks) following the earlier multi-vehicle collision.
“There is still approx. 4 miles of congestion on approach, please allow extra time for your journey.”
As of 11.34, the agency’s website said “there are currently delays of 10 minutes against expected traffic”.
Inrix reported earlier in the morning: “Two lanes blocked and queueing traffic due to accident, three cars and a van involved on M25 clockwise between Clacket Lane Services and J6 A22 ( Godstone ).
“Congestion to almost J5 (M26 interchange). In lanes three and four (of four), a mile after the services.”
The traffic and travel service added at 10.33am: “One lane blocked and queueing traffic due to recovery work and accident, three cars and a van involved on M25 clockwise between Clacket Lane Services and J6 A22 (Godstone).
“Congestion to almost J5 (M26 interchange). In lane four (of four), a mile after the Services.”
A spokesperson for Surrey Police earlier said: “We were called at 9.31am to reports of a four vehicle collision on the M25 between junctions 5-6.
“We attended alongside Highways England and the ambulance service but not aware of any fatality or serious injuries at this time.”
Normal traffic conditions are expected between 11.30am and 11.45am.