WATCH: A live feed of the 27-storey apartment block burning in London

Firefighters react as a huge fire engulfs the Grenfell Tower early June 14, 2017 in west London. Photo: Getty Images.

A massive fire has engulfed a 27-storey apartment block in West London.

Up to 40 fire engines and 200 firefighters are tackling the blaze at Grenfell Tower on the Lancaster West Estate in North Kensington.

Grenfell Tower/ Google Maps

“Firefighters wearing breathing apparatus are working extremely hard in very difficult conditions to tackle this fire,” London Fire Brigade assistant commissioner Dan Daly said. “This is a large and very serious incident and we have deployed numerous resources and specialist appliances.”

Crews responded to the blaze at 12.54am local time. The cause of the fire is not known, but the tower had been undergoing a major refurbishment.

The Metropolitan Police said “an evacuation process is under way” and there are fears the tower block would soon collapse. The fire has been declared a “major incident” by London mayor Sadiq Khan. Metropolitan police have closed the A40 is closed in both directions.

A number of people have been treated for injuries but there is no word yet on any fatalities. More than 200 people are believed to be residents in the tower, which contains 120 units, and there have been reports of people signalling SOS with their house lights before the fire engulfed the entire building. It’s not yet know how many people escaped the inferno.

There are many reports on Twitter from onlookers saying they could hear people in the tower screaming for help and eyewitnesses have subsequently said the saw people jumping from the building.

The London Ambulance service said it responded to the fire at 1.29am, sending more than 20 ambulance crews as well as hazardous area response crews.

The fire is believed to have started on the second floor and spread right to the top of the tower. (There are some reports the tower is 24 storeys high.)

George Clarke, the presenter of Channel 4 TV programme Amazing Spaces, told Radio 5 Live he could see what he thought were torchlights flashing in the upper floor.

“I’m getting covered in ash, that’s how bad it is,” he said.

“I’m 100 metres away and I’m absolutely covered in ash.”

As dawn approached, it looked like firefighters were slowly containing the blaze:

Good Morning Britain news correspondent Jonathan Swain said burning falling debris was making it difficult and dangers for firefighters, and he could see people trapped in the building.

By 5am London time, the blaze was largely under control.

London’s worst tower fire occurred in 2009, when six people lost their lives in the Lakanal House fire. The speed at which the block was engulfed saw all local authorities ordered to check the safety of high-blocks.

Just seven months ago, a group of residents called the “Grenfell Action Group” posted an article on their website suggesting the Royal Borough of Kensington and Chelsea council landlord has ignored their concerns about fire safety at the block.

In February, Southwark council, the landlord of Lakanal House, was fined £570,000 over fatal fire, which started in a television in a ninth-floor flat.

An earlier inquest found those who died had been told to stay in their apartment by fire officials who believed the block had adequate measures in place to protect them.

NOW WATCH: Briefing videos

Business Insider Emails & Alerts

Site highlights each day to your inbox.

Follow Business Insider Australia on Facebook, Twitter, LinkedIn, and Instagram.