A fuel tanker has crashed in a tunnel at the Dartford crossing leading to severe delays and congestion warnings.
The vehicle crashed in the west tunnel leaving the driver trapped with minor injuries on Thursday afternoon.
Kent Police told drivers to use the A2 and cross the river by using the Blackwall Tunnel or the Woolwich ferry, as an alternative route.
BBC travel reports warned of severe delays of up to an hour.
The accident led to the closure of both the east and west tunnels, but one has since reopened.
A Kent Police spokesman also said: "The incident has caused serious congestion and traffic heading for the Dartford Tunnel is advised to use the A2 into London and use the Blackwall Tunnel or the Woolwich Ferry as a crossing point."
The driver was thought to have suffered minor injuries, he added.
Emergency crews gave the driver first aid before paramedics arrived, and worked to remove the vehicle from the tunnel.
BBC Travel news said the eastern tunnel had reopened by 1525 BST but the west bore, where the accident happened, remained closed.
There were reports of severe delays of up to an hour, with stationary and queuing traffic. All traffic was at a stand at the toll booths, travel reports added.
The Dartford crossing carries about 150,000 vehicles each day.