The Blackwall Tunnel on the A102 has been closed for more than five hours following a crash.
The road is closed northbound and only one lane southbound is open due to a collision at 1.30am on Wednesday, however, no further information on the incident has been confirmed.
Drivers have been warned of long delays and told to use an alternative route.
Transport for London (TfL) said: “Northbound traffic is tailing back to Falconwood and southbound is down to one lane with tailbacks to Woolwich flyover.”
The tunnel is closed from the A2, Sun In The Sands Roundabout, Blackheath, to the A206, Woolwich Road Flyover, Greenwich.
London bus routes 132 and SL4 are being diverted, with TfL stating route SL4 is on diversion in both directions while the 132 is being diverted northbound.
Passengers are being urged to allow extra time for their journeys.
