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Traffic was temporarily stopped near the Dartford Crossing after a serious collision between two lorries on the M25.
Motorists heading towards the bridge were being held on the A282 Essex-bound approach to the tunnels just before the evening rush hour.
It came after a collision on the M25 anti-clockwise link between J31 and J30.
A National Highways spokesman said: "Traffic is being held whilst closures are installed. Please allow extra travel time."
An Essex Police spokesman said: "We’re on the scene of a collision close to junction 30 on the anticlockwise M25 which involves two lorries.
"A road closure is in place from junction 31 whilst the incident is being dealt with."
As of 8.30pm, congestion had eased and the road was starting to clear.