LONDON, England (CNN) -- A thick plume of black smoke covered the sky over London Monday as blaze broke out in a disused warehouse on the site of the 2012 Olympics. Fire crews were investigating the cause, but it was not thought to be terror-related.
An image of the blaze taken by CNN viewer Mo Helmi from her apartment in north London.
The London Ambulance Service said there were not thought to be any casualties from the blaze, which started at around 12:15 p.m. local time.
At least 15 engines and 75 firefighters were called in to tackle the height of the blaze in a disused warehouse in the east of the city.
A thick column of black smoke, believed to have been caused by burning diesel fuel, could be seen for miles over the city.
The Olympic Delivery Authority, coordinating construction for the 2012 Games, said the fire was located within the Olympic site, behind a bus depot.
The fire sparked initial alarm in London, which was targeted with deadly attacks by Islamic extremists in 2005, but police said it was not thought to be terror related.. Watch column of smoke over the city »
The site of the fire was less than a mile from Stratford International, a station serving the Eurostar train. It is also close to the Canary Wharf business district and London's City Airport -- which was not affected.
Paul Smith, who manages a print business near the blaze site said the bus depot had been closed since July and was being redeveloped for the Olympics. He said emergency services had evacuated some nearby buildings.
"The sky overhead is totally overcast. It's like twilight round here," Smith told CNN. "The police have moved people out of some places. We are still here, though."
Another eyewitness David Buik, who was watching the blaze from his offices in Canary Wharf, said the fire was producing acrid smoke.
"It must be something chemical or oil, it is rancid." E-mail to a friend