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Seven cars have been damaged by a hazardous pothole.
Kent Police and highways teams closed part of the southbound carriageway near Tonbridge at around 6am.
Kent Police said it was called out at 6am, Highways England, the authority responsible for the road, was not aware until just after 9am.
A Highways England spokesman said: "This incident was referred to us at 9.15am. We have put a lane one closure in place for the recovery and repair of seven vehicles."
No one was injured and only one lorry remains at the scene.
A Kent Police spokesman said: "Officers and highways teams are at the scene where part of the carriageway has been closed at the Quarry Hill junction to allow repairs to be completed."
The road will reopen once Highways England completes repair works on the road.
The closure is causing heavy traffic in and around Tonbridge.