London’s fire Commissioner has said there have been some fatalities in the massive apartment building fire that erupted in the wee hours Wednesday and around 50 people have been taken to hospitals for treatment.

Police received report of the fire at the Grenfell Tower on the Lancaster West Estate in North Kensington at 01:16 local time (0016 GMT). The apartment block, built in the 1970s and renovated several times, has 120 apartments.

Seven hours later, most of the building has been reduced to a blackened hulk. Forty-five fire engines and 200 firefighters are continuing to battle the blaze. Helicopters have also been deployed to the site for rescue operation.

London Ambulance Service confirmed that they have taken 50 victims to five hospitals. Firefighters at the scene said they had managed to evacuate residents up to the eleventh floor.

Police were also clearing out nearby buildings as large pieces of debris were seen falling from the building. Eyewitnesses have reported seeing people inside the building while the fire raged.

Mayor of London, Sadiq Khan called the fire a “major incident.” The cause of the blaze remains unknown.