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Traffic was halted at the Dartford Crossing after a woman threatened threatening to jump from the QEII Bridge.
Police closed the route at 4.30pm, with witnesses saying the woman had been seen on the other side of the barriers.
Highways England said: "Traffic is held on approach to Dartford Crossing ... we expect traffic released very shortly. "
Traffic was flowing again by 5pm. A lifeboat was launched but was not needed and the woman was taken into the care of police.