The Blackwall tunnel in A102 has been closed for more than five hours after an accident.
The road is closed to the northern border and only one southern line to the border is open due to collision at 1.30 on Wednesday morning, but no other information has been confirmed.
Drivers have been warned of long delays and are said to use an alternative route.
Transport for London (TFL) said: “North traffic goes back to Falconwood and Southbound turns to a back -to -flight line to Flyover Woolwich.”
The tunnel is closed from A2, the sun on Roundabout Sands, Blackheath, to A206, Flyover Road Woolwich, Greenwich.
The London bus routes 132 and SL4 are diverting, with TFL indicating that the SL4 route is deviant in both directions while 132 moves north on the border.
Passengers are asked to take extra time for their trips.
