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Traffic is using the hard shoulder to get out of queues caused by a crash between a car and a lorry near the Operation Brock contraflow.
Motorists were seen driving the wrong way to avoid delays after a lorry reportedly overturned, spilling its fuel, on the M20's coastbound carriageway between Junction 8 for Leeds and 9 for Ashford.
A specialist recovery vehicle is now on the scene to remove the lorry and travel time is 90 minutes.
One motorist said they had not moved their car for an hour and was "stuck".
Highways England has now announced traffic is passing past the scene of the collision.
A statement on Highways England said: "Traffic caught within the contraflow lane of the #M20 J8-J9 is being allowed past the scene of the collision in one lane.
"Once traffic cleared from the contraflow lane it will be closed. All traffic will be routed via the coastbound carriageway."
Lorries are supposed to queue on the coastbound carriageway during Operation Brock, rather than use the contraflow system.
Kent Police officers were called to the scene at 5.24pm, where they were joined by Secamb and Kent Fire and Rescue Service.
Witnesses have reported seeing up to five ambulances and four fire engines travelling along the contraflow system.
Another eye witness said he saw at least five cars driving the wrong way up the Junction 7 entry slip at Detling to get off the motorway and avoid delays.
Operation Brock splits what is normally the London-bound carriageway in half so traffic can travel in both directions via two lanes.
The coastbound carriageway is then used for queuing lorries.
A spokesperson from Kent Police said: "The coastbound carriageway (within the contraflow) is currently closed to traffic and drivers may wish to consider alternative routes."
One person has been treated for injuries which are not thought to be life threatening.
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