Firefighters are now battling a huge blaze that has broken out at the Mandarin Oriental Hyde Park in London.
Guests and staff were evacuated from the luxury Mandarin Oriental Hotel in Knightsbridge as 120 firefighters tackled a large fire on the roof.
Eyewitness Sarah Bashir filmed footage of smoke rising from the 12-storey Mandarin Oriental Hotel in the exclusive Knightsbridge area of the city.
Less than an hour after the London Fire Brigade was called to the scene, the amount of smoke billowing from the hotel's roof had been greatly reduced.
The fire service said the blaze was "producing a lot of smoke" and was "very visible" and its cause "is not known at this stage".
The cause of the fire is not yet known, a spokesperson confirmed.
A Mandarin hotel group spokeswoman said that work on the building was still being carried out.
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With nearly 200 rooms, the hotel is located near Harrods department store in Knightsbridge, an upmarket area of central London.
20 fire engines have been sent to the Mandarin Oriental hotel in William Street, Knightsbridge, near the capital's West End. In a statement, the London Fire Brigade said: "The brigade was called at 3.55pm". "Firefighters are working extremely hard to bring the fire under control".
Another worker, who asked not to be named, said: "The fire alarm started and everybody was told to get outside".
The hotel overlooks Hyde Park and is located less than a mile away from the Harrods and Harvey Nichols department stores, and Buckingham Palace.
Penelope Evans, 50, from Battersea in south London, was leaving Harrods when she noticed the blaze.
"I saw all this black smoke coming from the sky, it was covering everything and the smell was horrendous".
The hotel says it is "aware of a situation". In 2011 the Queen hosted an event there for foreign and British royalty on the night before her grandson, Prince William, got married.