An earlier crash part blocked a motorway and closed one of the Dartford Tunnels.
Traffic is reportedly queueing after an accident between a van and car on the M25 anticlockwise.
The incident was at the Dartford Tunnel between junction 1a for the A206/A226 and junction 31.
Traffic England says it is taking about half an hour to get through the delays during rush hour.
A spokesman for Kent Police said: "Kent Police was called to the scene at 3.07pm. The South East Coast Ambulance Service was also called.
No serious injuries have been reported and motorists are advised to expect delays.