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The emergency services, including the air ambulance, were called to the scene of a crash in Rainham.
The accident involved a car and a motorbike at the end of Otterham Quay Lane which is closed from the A2 to the junction of Ten Acre Way.
Officers were called at 2.57pm and the road has been closed to keep motorists and emergency services personnel safe.
A witness said: "I didn't see what happened but several people had stopped to help the casualty and call the emergency services. The air ambulance landed in a field next to the road and was there for about half an hour before leaving."
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