Emergency services including Surrey Police, Fire & Rescue and Ambulance Service have rushed on the spot to assist.
Resources of National Highways are also on the spot, assisting with traffic management.
The incident is causing approximately eight miles of congestion from J9, at Leatherhead, adding at least two hours to normal journey times.
Only one lane remains closed at the moment, however it is not known when the delays are expected to improve.
National Highways said: “Delays are severe due to the initial response of the emergency services requiring multiple lanes to be closed to traffic.”
They added: “Please allow plenty of extra journey time for journeys along the M25 anti-clockwise in Surrey or in the local area.
“You may wish to consider alternative routes or to delay your journey.”