A helicopter crashed into a crane on top of one of Europe's tallest residential blocks on Wednesday, killing two people as it burst into flames and threw plumes of smoke into the foggy air above central London.
Police said there was nothing to suggest a terrorism link to the crash on the south bank of the River Thames in the British capital, where 52 commuters were killed in rush hour suicide bombings in 2005.
"There was a really loud bang," said Julie Marsden, who works in an office building near the crash site which is close to landmarks such as the headquarters of Britain's MI6 international intelligence agency and the Houses of Parliament.
"We saw the crane fall to the ground and this massive plume of black smoke," Marsden told Reuters.
Witnesses said the helicopter hit the crane on top of the as yet unoccupied 185-metre (200-yard) high cylindrical block - The Tower, One St George Wharf - span out of control, fell to the ground and burst into flames, setting nearby buildings alight.
There was wreckage and debris strewn across roads close to Vauxhall train station, a major transport hub on the south side of London, which was packed with thousands of commuters at the time of the incident shortly after 0800 GMT.
A Reuters reporter at the scene said tangled bits of crane could be seen hanging off the side of the tower, the top of which was still shrouded by low cloud an hour after the crash.
Police Commander Neil Basu said the helicopter was on a commercial flight from Redhill, south of the capital, to Elstree, home to famous British film studios in north London, but had been diverted to a heliport near the crash site.
He said there were 11 casualties including two dead and one critically injured. The emergency services said the pilot was one of those killed and it was not thought anyone else was on board. The other fatality was found near the wreckage and the fire service said it had rescued a man from a burning car.
The helicopter involved was an Italian-made AgustaWestland 109, the company's best selling VIP corporate helicopter, according to a source familiar with the situation. The twin-engined helicopter can carry eight passengers.
Out of control
Rezart Islami a construction worker from Kosovo who had been on a nearby site, said he saw the helicopter flying fast up the river before it smashed into the crane which then fell and hit two cars.
"I was shocked, it was spinning around and lost control," he told Reuters.
Another witness, Edmir Pishtar, who was in a van outside the building site, said he saw half the crane crash down and cut into two cars on the road. He later spoke to the operator who was about to get inside the crane cab.
"He was literally shaking because he was getting ready to climb into the crane and he was late," Pishtar said.
The Tower, One St George Wharf, is described on its website as the epitome of luxury London living, with 360-degree views across the capital and over the Houses of Parliament.
Builder Brookfield Multiplex said the tower, which is not occupied and is under construction, has 52 floors and houses 212 luxury apartments. Media reports in recent years have suggested the Penthouse apartments could go for as much as 50 million pounds ($80 million).
"Fortunately for us we have done a full headcount and there are no injuries or fatalities among anyone on the site," said Tony Pidgley, chairman of the tower's developer Berkeley Group .
"The crane driver normally starts at eight o'clock but unusually, today of all days, was late."
He said it was too early to speculate on the cause of the crash but helicopters should normally fly 500 feet (150 metres)above tall structures.
Police were questioning witnesses in the area and dozens of emergency vehicles were in attendance, Reuters reporters said. Roads around the area including a route over the Thames were closed off, and bus and rail services were affected.
"There's nothing to suggest any terrorism link," a spokesman for London's Counter Terrorism Commandsaid. The fire service said eight fire engines and 60 firefighters were on the scene.
Helicopters in London are generally supposed to fly along the River Thames but London City Airportsaid its flights had been disrupted due to low visibility.
The Department of Transport's crash investigation unit said it was preparing the launch an inquiry into the incident. ($1 = 0.6215 British pounds)