Lower Thames Street was completely closed near London Bridge as a huge number of emergency vehicles arrived in the area from 11.30am.
Armed police swoop on City of London as incident declared
Officers with hand guns in holsters were seen directing traffic as a large area, including a footbridge, was sealed off just east of the junction with Fish Hill Street- writes express.co.uk.
It is understood a man fell from a pedestrian footbridge and was left with head and chest injuries.
London Ambulance service paramedics were also on the scene treating the casualty, who was seen laying on the ground.
Transport for London tweeted: "Due to emergency services dealing with an incident. Lane oen of two is closed on A3211 Lower Thames Street just before London Bridge heading towards Blackfriars. Traffic is slow on approach."
City of London Police tweeted: "Upper Thames Street is currently closed. We are on the scene with the @Ldn_Ambulance Service and will update you when the road is re-opened."
Traffic tailbacks were forming as crowds gathered to watch what was happening.
It is understood the person was injured, but survived the fall.
Several ambulance staff were crowded around the person on the floor who appeared to be covered in a blanket.
There were four London Ambulance Service vehicles on scene, several police vehicles and the London Air Ambulance was also dispatched.
A City of London Police spokeswoman said: "We were called at 11.35am today to an incident on Upper Thames Street, where a pedestrian had fallen from the footbridge.
"Officers were at the scene with London Ambulance Service. Upper Thames Street was closed.”
At just before 1pm the road was re-opened.
The spokeswoman added: "The pedestrian has now been taken to hospital."
Thames Street, divided into Lower and Upper Thames Street, is a main route through the City of London financial centre, which brings traffic in from East London.
It forms part of the major A3211 route from Tower Hill to Westminster.
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