There is a fire outbreak at the central London hotel the Mandarin Oriental, sending large plumes of smoke billowing above the capital.

The London Fire Brigade (LFB) said it had sent 20 fire engines and 120 firefighters to the blaze in Knightsbridge.

A brigade spokeswoman said no details were available yet on whether anyone was trapped, but a later statement said a “systematic search” was underway.

Staff have been evacuated to Hyde Park, alongside some people from neighbouring buildings.

LFB was first called to the William Street hotel at 3.55pm. Fire crews from Kensington, Hammersmith, Battersea and Chelsea were sent to the 155-year-old, 12-storey hotel, which is near Hyde Park, it said.

Transport for London said the Sloane Street entrance to Knightsbridge station was closed at the request of emergency workers. Passengers should use the Harrods entrance instead, the body said.

The cause of the fire is unknown and LFB crews “are likely to be on the scene throughout the night”, the body said.

A column of dark smoke could be seen billowing from the upper levels of the period hotel, which has 181 suites and is between Hyde Park and Knightsbridge’s shopping district, which includes Harrods.

The building underwent an “extensive restoration” ending late last month and costing several million pounds, its owner company Mandarin Oriental Hotel Group said in May.

London Ambulance Service could not say whether it had treated any patients or how many paramedics it had sent to the scene. More information would be released later, a spokeswoman said.

The Metropolitan Police is also on the scene.

The hotel is connected to the prestigious One Hyde Park development, which boasts the most expensive addresses in London.

The apartments have been known to go on the market for as much as £75m and guests can use the facilities at the neighbouring hotel, such as the private cinema. They can also order room service from Heston Blumenthal’s restaurant ‘Dinner’ – famous for its innovative menu.

Emergency services, including fire engines and ambulances, were still arriving at around 4.45pm. Flames could be seen around the top of the hotel, and extended ladders were erected to access that area of the building.

A local businesswoman, who asked not to be named, said: “The fire was in the middle of the Mandarin Oriental Hotel. There was a lot of smoke. I couldn’t see anyone being evacuated but they had closed off the whole road.

“It’s quite a lot of smoke, you could smell it. I could see a lot of fire engines and police cars and some ambulances as well.”