A massive plume of black smoke has spread over London from a large warehouse fire on the site for the 2012 Olympics.
Smoke is visible across London
Firefighters have confirmed the smoke contains asbestos. People with respiratory conditions have been advised to stay indoors.
An investigation into the cause is underway, but early indications are it is an accident rather than arson.
The fire on the western edge of the Olympic Park, near Stratford, in the east of the capital, was tackled by at least 75 firefighters.
London Fire Brigade Assistant Commissioner Dave Brown said: "There was asbestos reported and large plumes of smoke, but the fire brigade acted very quickly to suppress the plumes of smoke and help local residents."
"The investigation into the cause is still ongoing and not thought to be suspicious."
No casualties have been reported.
Hundreds of workers were evacuated from nearby buildings.
The bright weather conditions meant the huge black cloud was visible over large areas of London.
Paul Hallam, 50, a production worker at a nearby printing firm, saw the fire take hold.
He said: "There were flames coming about 100ft high in the end. The whole of that building, about the size of a football pitch, went up. We could feel the heat through the glass."
Dr Keith Prowse, chairman of the British Lung Foundation, said: "It's not clear what the smoke fumes or particles contain.
Huge blaze near Stratford
"We would, however, advise anyone in the area who has a respiratory condition to stay indoors as the smoke could cause them problems."
The centre of the fire was in a disused building off Waterden Road, which was about to be demolished as part of the 2012 Games.
The high-speed Channel Tunnel rail link runs nearby.
A Eurostar spokesman said the incident has not affected the new High Speed One line, which will begin carrying European services on Wednesday.
There has been no disruption to flights from nearby London City Airport.
Firefighters are expected to be on site overnight to ensure the fire is damped down properly due to the possibility of hot spots flaring up.
Currently 20 traveller families live at Waterden Crescent off Waterden Road. They are due to be moved as their site is in the Olympic Park.