The death toll in a fire disaster that destroyed a 24-storey block of flats in London was expected to rise on Thursday, with many people still missing and firefighters facing hazardous conditions as they searched the charred carcass.

Flames leap from a tower block severely damaged by a serious fire, in north Kensington, West London.

Smoke was still wafting out of the shell of the Grenfell Tower on Thursday morning and a Reuters witness saw a big piece of cladding falling from the building, 32 hours after fire engulfed the building in the early hours of Wednesday and turned it into a huge flaming torch in minutes.

Authorities have confirmed 12 deaths but have said that the figure would rise and that they did not expect to find any survivors. Firefighters rescued 65 people from the building.

London Fire Brigade chief Dany Cotton told ITV that her crews had reached the top floor of the building and conducted initial visual searches from doorways but had not done a comprehensive search because it was unsafe.

"We've got structural surveyors and my urban search and rescue team who are going to come down, make an assessment and find a way of making the building safe so that we can go through the whole building, fingertip search, painstakingly, looking to see what's in there," she said.

Prime Minister Theresa May was expected to visit the scene on Thursday, Sky News reported, citing unnamed sources. May's Downing Street office had no immediate comment.

Survivors who have lost all their belongings in the blaze spent the night at emergency shelters, as charities and local support groups were flooded with donations of clothes and bedding from shocked Londoners.

The fire brigade said the inferno was unprecedented in its scale and speed.

"The scene that I was confronted with was an unparalleled scene to anything I had seen before. The building was ablaze. I have truly never seen that in a high-rise building," Cotton told Sky News.

CAUSE UNKNOWN

The tower, a social housing block built in 1974 in North Kensington, an area of west London, contained 120 flats and was thought to have been home to about 600 people.

Harrowing accounts emerged of people trapped inside as the blaze destroyed everything around them, shouting for help and trying to escape through windows using makeshift ropes from bed sheets tied together.

By Thursday morning, there was no sign of life in or around the blackened hulk. Security cordons were in place around the base of the tower, where the ground was littered with charred debris.

Outside the cordons, impromptu tributes had appeared, with photos of missing people, messages of condolences, flowers and candles.

Emergency services said it was too early to say what had caused the disaster. Some residents said no alarm had sounded. Others said they had warned repeatedly about fire safety in the block.

The building had recently undergone an 8.7 million pound ($11.1 million) exterior refurbishment, which included new external cladding and windows.

Planning documents detailing the refurbishment did not refer to a type of fire barrier that building safety experts said should be used when high-rise blocks are being re-clad, according to Reuters research.

Source: Reuters