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Drivers heading from Kent to Essex are facing long delays tonight following two separate crashes.
Four cars are understood to have been involved in the collisions on the anticlockwise stretch of the M25 approaching the Dartford Crossing.
The accidents happened near to junction 1A at Swanscombe at 5.30pm and caused tailbacks to junction 3 the Swanley Interchange.
One of the tunnels had to be closed for a time and some drivers say it is taking several hours to get through the backlog of traffic.
A broken down lorry between junctions 1B and 1A has been adding to the congestion.
All lanes re-opened at 6.50pm but it may take some time for the delays to clear
Earlier in the day sheer volume of traffic also caused lengthy queues approaching the tunnels.
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