Multiple fatalities have been confirmed after a massive fire broke out in a 24-floor block of flats in west London with witnesses claiming residents are trapped inside.

The London Fire Brigade said 40 fire engines and 200 firefighters were battling the blaze which had engulfed all floors from the second to the top of the Grenfell Tower in the north Kensington area in the early hours of Wednesday.

"Unfortunately, there have been a number of fatalities," Danny Cotton, Commissioner at London Fire Bridage, said. "I can't confirm the figure due to the size and complexity of the building.

"It's a major fire that has affected every floor from the second floor upwards."

More than 50 people were taken to hospital, according to London Ambulance Service.

Flames ravaged the tower, lighting up the pre-dawn west London skyline and sending up a thick plume of black smoke. Flumes of black and grey smoke billowed into the air over London hours after the blaze was sparked.

Large pieces of debris could be seen falling from the building.

"A number of people being treated for a range of injuries," police said.

It has emerged that residents of Grenfell Tower voiced concerns about the building's fire safety last year.

"It is a truly terrifying thought but the Grenfell Action Group firmly believe that only a catastrophic event will expose the ineptitude and incompetence of our landlord, the KCTMO, and bring an end to the dangerous living conditions and neglect of health and safety legislation that they inflict upon their tenants and leaseholders," members of the Grenfell Action Group said in a blog dated November 2016.

The group has since posted a new entry on its blog, saying "all our warnings fell on deaf ears".

"We predicted that a catastrophe like this was inevitable and just a matter of time."

It is our conviction that a serious fire in a tower block or similar high density residential property is the most likely reason that those who wield power at the KCTMO will be found out and brought to justice."

No KCTMO official was available for comment.

Witnesses said they heard screaming from the upper floors as the flames rose in the night.

"They were trapped. They couldn't come downstairs, especially from the top floor ... People have been burned," a witness identified as Daniel told BBC Radio London.

"I have seen it with my own eyes. And I have seen people jump."Hanan Wahabi, 39, told AFP news agency she escaped with her husband and son, 16, and eight-year-old daughter but feared for her brother and his family who live on the 21st floor.

"Last time I saw him they were waving out the window, his wife and children," she said.

"I've not heard from them since, the phone is not going through, the landline isn't going through."

Al Jazeera's Laurence Lee, reporting from London, said "there were serious and long-standing complaints by the residents".

"This is being described as a potentially catastrophic event," he said.

Trapped inside

Witnesses at the scene confirmed hearing people screaming for help from inside the building and also tying towels and bedsheets to try and escape from the windows before being advised against doing that by the police.

"The entire building is on fire, the flames are going from the ground to the roof," Jeff Howard, a witness, told Al Jazeera.

"The flames are now making their way around the building, almost to the point where they are coming together. I heard helicopters over my building around 1:45am and there was a bit of screaming outside."

Police said in a statement they were called at 1:16am (0016 GMT) "to reports of a large fire at a block of flats in the Lancaster West Estate".

Mayor of London Sadiq Khan said a "major incident" had been declared.

Al Jazeera's Mina Harballo, reporting from London, said the main worry for the fire fighters was the people still inside the building,

"The lifts stop working when there's a fire so there might be some people, including the elderly still stuck inside the building," she said.

"Police have evacuated houses around the building and we've heard from fire fighters."

PHOTO CAPTION

Flames and smoke billow as firefighters deal with a serious fire in a tower block at Latimer Road in West London, Britain June 14, 2017. REUTERS

Al-Jazeera