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An earlier crash part blocked a motorway and closed one of the Dartford Tunnels.
Traffic was queueing after an accident between a van and car on the M25 anticlockwise.
The incident was at the Dartford Tunnel between junction 1a for the A206/A226 and junction 31.
Congestion also built up on the M25 before junction 3 for the M20.
A spokesman for Kent Police said: "Kent Police was called to the scene at 3.07pm. The South East Coast Ambulance Service was also called.
"The collision took place in the East tunnel."
The road has since reopened and delays have now cleared.
No serious injuries have been reported.