A massive fire broke out at Mandarin Oriental Hyde Park hotel in London on Wednesday. London Fire Brigade said that about 120 firefighters and 20 engines are at the spot.

Plumes of smoke were seen after which the fire department was informed at 4 pm. Flames could be seen around the top of the hotel, and extended ladders were erected to access that area of the building. 

In a statement, the London fire brigade said: "The brigade was called at 3.55pm. Fire crews from Chelsea, Kensington, Hammersmith, Battersea and other surrounding fire stations are at the scene. The cause of the fire is not known at this stage."

Guests climbed several floors down external fire escapes for getting away from thick black smoke billowing above them.

The incident comes a week after the completion of "the most extensive restoration in the five-star hotel's 115-year history," BBC reported.

Police said the hotel was being evacuated and it was not yet known whether there had been any injuries. The cause of the blaze was not yet known.

The guests and staff were evacuated to Hyde Park, where they were given bottles of water.

The five-star hotel is located in the Knightsbridge district of London, and is owned and managed by Mandarin Oriental Hotel Group. The hotel has 173 rooms and 25 suites, over half of which overlook Hyde Park.