Two people have died after a helicopter crashed into a crane at a building site in central London in misty conditions, police have said.
Police said it appeared the helicopter had hit the crane on top of a building at about 08:00 GMT.
London Fire Brigade said the crash happened near Wandsworth Road in South Lambeth and 60 firefighters were there.
Burning wreckage lay in the road, with all approaches to the Vauxhall Cross one way system closed.
The incident caused gridlock as roads were closed at the height of the rush hour and Vauxhall Tube station and railway station have been closed.
‘Enormous bang’ The fire brigade was also attending a second scene involving a crane in a precarious position on St George’s Wharf.
Video footage shot on a mobile phone showed an entire road blocked by burning wreckage and aviation fuel.
Eyewitness Chris Matthison: “There was an unusual buzzing sound and a dull thud”
The side of a building on one side of the street was also damaged by the flames.
Passers-by stood watching as the wreckage burned. A motorcycle was also lying on its side in the road where it was abandoned.
Ex-BBC producer Paul Ferguson said the helicopter “plummeted straight into the ground”.
He said: “The building the helicopter hit is shrouded in mist.”
He said the crane at the top of the building was now hanging down the side of the building.
Nicky Morgan, MP for Loughborough, witnessed the crash.
‘Huge smoke cloud’ “I was walking towards Vauxhall tube station from Lambeth Palace area where I have a flat,” she said.
"There was suddenly an enormous bang - I thought something exploded.
"It was coming from beyond Vauxhall tube station.
Vauxhall is one of the busiest parts of central London for road and rail traffic.
The area was cordoned off as emergency vehicles went to the scene of the crash.
Police said a “major critical incident” had occurred, as cars were turned back.
There were large tailbacks as commuters sought alternative routes through Chelsea, while Vauxhall Bridge was closed to cars and bicycles.
Crowds of people stood across the Thames to watch as police and ambulance boats rushed towards the crash site.
"Then clouds and clouds of black smoke.
"I presumed what it was I heard was the crane collapsing or the helicopter crashing into it.
“I heard the bang then saw the clouds of smoke but there was too much in the way to see much at that point.”
Some witnesses reported the wreckage hitting two cars.
Witnesses reported seeing debris on the ground.
Quinn Murray was cycling when he saw the crash.
He said: "I saw the helicopter hit the top of the crane and come down just to the left of the station.
"There was quite a large amount of fire and a huge smoke cloud. It wasn’t on the road, but into a building site where they are building the new Nine Elms area.
“There’s a huge number of emergency services.”
Eyewitness Chris Matthison told BBC News: "There was some damage to the crane.
It’s possible the crane is lying across Nine Elms road.
"The top of the nearest building is steeped in mist and difficult to see.
"I heard a very unusual dull thud, then there was silence. The silence really took my imagination. Emergency services responded very quickly