Two people have died and 13 were injured after a helicopter crashed in central London this morning when it hit a crane on top of a tower block by the River Thames.
The stricken aircraft cartwheeled to the ground and exploded into flames before crashing into a street during the rush hour.
Burning wreckage and aviation fuel covered the road as eyewitnesses reported seeing cars on fire and hearing people screaming. Two people have been taken to hospital.
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David Cameron said after the tragedy that the issue of helicopters flying over central London needs to be examined, as astonishing eyewitness accounts emerged from the horrific crash.
It was revealed this afternoon that the crane operator only survived the crash because he was running late and was not in his cabin when the aircraft came down.
London Mayor Boris Johnson, who visited the crash site on Wednesday afternoon, said the crane has since been 'safely secured'.
The pilot killed when the helicopter came down was named this afternoon as Pete Barnes.
The 'respected and well-liked' contract pilot had previously flown a number of celebrity clients and also worked on several Hollywood films.
London Fire Brigade station manager Bruce Grain, one of first firefighters at the scene, said it "was absolute chaos" but he revealed the fire was put out within 20 minutes.
Eight fire engines, four fire rescue units and around 60 firefighters plus officers attended the scene of the crash, a few hundred yards from MI6, on a busy road.
Firefighters rescued a man from a burning car and brought a blaze caused by the crash under control.
Four fire engines and two fire rescue units also attended reports of a crane in a precarious position. The brigade was called at 8am.
The crane was on top of a building called The Tower in the St George Wharf development, and is billed as one of Europe's tallest residential towers.
A spokesman for London Fire Brigade said: "We are taking lots of emergency calls at the moment".
One eyewitness reported seeing cars on fire and hearing people screaming.
As rush-hour traffic built up, the A3036 Wandsworth Road in Vauxhall was closed in both directions between Vauxhall Cross and the Lansdowne Way junction.
Flying conditions this morning were reflected in the fact that London City Airport in Docklands had delays due to poor visibility.
Paul Ferguson, who was working in an office near the incident, told BBC News: "There was a flash and the helicopter plunged to the ground. It exploded and you can imagine the smoke coming out of it.
"It was probably heading from the nearby heliport. It may be that on this misty morning the lights on nearby St George's Tower weren't on and it moved and clipped the edge of the crane and lost control."
Related slideshow: Helicopter crashes in Central London during rush hour covering road in burning fuel
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."
He added: "I heard a very unusual dull thud, then there was silence. The silence really took my imagination. Emergency services responded very quickly."
Transport for London said buses in the Vauxhall area were subject to diversion and delays due to the incident. People were advised to avoid the area and seek alternative routes.The aircraft is understood to be an AgustaWestland AW109, a lightweight, twin-engine helicopter with eight seats.
The Met Police said they were "aware" of 11 casualties, including two dead.
One person was taken to a south London hospital in a critical condition, three people suffering minor injuries were taken to south London hospitals and five people were treated at the scene for minor injuries.
Met Commissioner Sir Bernard said: "We believe at the moment there are something in the order of 11 casualties and the other reason we're a little unclear is because people are presenting to different places trying to get help."
There was some confusion around the number of people in the aircraft, although it was earlier reported that it was flying between Gatwick and Elstree with two on board.
However, a spokesman for the RNLI said London Coastguard was contacted by Battersea London Heliport, which confirmed it had lost contact with one of its aircraft.
A lifeboat was launched from the Tower RNLI lifeboat station to search the Thames but is understood to have since stood down.
Traffic chaos broke out in the wake of the incident, with Vauxhall Bridge Road southbound closed, Wandsworth Road partially closed, Nine Elms Lane partially closed and South Lambeth Road partially closed.
Vauxhall Tube, train and bus stations are also currently closed.
Cloud in central London was very low at the time of the accident, according to MeteoGroup, the weather division of the Press Association.
Forecaster Paul Knightley said London City Airport was reporting a cloudbase of just 100ft (30.5m) at 8am.
"The top of the building would have been shrouded in cloud," he said.