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Traffic was held on the M25 QE2 Bridge at Dartford after reports of a man on the crossing.
Essex Police reported on Twitter that officers are on the scene but were likely to be some time, and warned drivers to avoid the area.
Traffic was stopped on the clockwise carriageway and tailbacks were building in the area.
As a result of the bridge closure, the two tunnels at the Dartford Crossing were used to take traffic in each direction.
Essex Police confirmed they were called to concerns for the welfare of a man on the Dartford Crossing shortly after 2.50pm.
They said emergency services attended and were working to resolve the situation as quickly and safely as possible.
Police also thanked drivers for their patience and understanding.
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