Tower Bridge is completely closed while police and firefighters deal with an injured person.
The London Fire Brigade (LFB) is at the scene and assisting paramedics.
City of London Police said the bridge is closed in both directions whilst they deal with an accident.
They are also urging drivers to avoid the area
Transport for London (TfL) said Westbound traffic is slow and there are queues approaching Glamis Road.
There is also congestion northbound with queues reaching the Bricklayers Arms Roundabout.
One Twitter user said the bridge was on lock down.
Tower Bridge on lockdown with multiple police, fire and ambulance crews on the scene.
Boats are still passing through so appears to be road related.