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One lane of the Dartford crossing was closed due to a crash as MP Chris Grayling prepared to make an announcement there about the Lower Thames Crossing.
Two vehicles collided on the QEII bridge, heading into Kent from Essex, at about 3pm.
Highways England said one lane was closed while the vehicles were recovered.
The lane is now open but queues have built up and there are still long delays in the area.
Mr Grayling is due to speak near the crossing this afternoon following this morning's Government announcement that a slightly adapted version of Option C had been chosen.
A tunnel and associated link roads will pass to the east of Gravesend and into Essex.
Delays were still being reported after 9pm.