LONDON (AP) — More than 100 firefighters were sent to tackle a blaze at a luxury hotel in London that produced thick black smoke visible for miles around Wednesday.

London Fire Brigade said it was called just before 4 p.m. (1500 GMT) to the 12-story Mandarin Oriental Hotel. Less than an hour later, 20 engines and 120 firefighters were at the scene and the amount of smoke billowing from the hotel's roof had been greatly reduced.

The cause of the fire was not yet known. There were no immediate reports of injuries.

The major road in front of the hotel in London's ritzy Knightsbridge was closed, causing rush-hour traffic chaos in that part of London.

Mandarin Oriental said that "as the situation is still unfolding, we have no further details to share at this time, but will provide an update soon."

The ornate Edwardian building near Hyde Park opened as a hotel in 1902 and recently underwent extensive renovations.

Writer Juno Dawson tweeted: "Well that was drama. The Mandarin Oriental is literally on fire. Evacuated mid photoshoot. Hope everyone is ok. It was the construction site on the roof that seemed to be on fire."