More than 30 people have been taken to hospital and a number of people are thought to be dead after an "unprecedented" catastrophe at a London tower block. 

Fire engines were on the scene in less than six minutes after calls began flooding in at 12:54am, with the flames spreading from the second to 27th floors of the tower block.

London Fire Brigade Commissioner Dany Cotton said she has 'never ever seen anything' of the scale of the blaze at Grenfell Tower. 

Fire Commissioner Cotton said: "This is an unprecedented incident. 

"In my 29 years of being a firefighter I have never ever seen anything of this scale. 

"Firefighters are working very hard at the moment. 

"This is a major fire that effected all floors of this 24-storey building from the second floor upwards. 

"I have over 200 of my firefighters and officers attending this incident, with 40 fire engines and a range of specialist vehicles, including 14 fire rescue units. 

"We declared this a major incident very early this morning, the first call coming in at 12.54. 

"Our first fire engines were on the scene in under six minutes." 

The fire is still burning more than seven hours later, and a cordon remains around the building amid fears it may collapse. 

There are flats on 24 of the 27 floors of the building, housing more than 300 people. 

Commissioner Cotton added: "Crews wearing breathing apparatus and extended duration breathing apparatus have been working in extremely challenging and very difficult conditions to rescue people and bring this major fire under control. 

"London Ambulance Service have confirmed that 30 people have been taken to five hospitals. 

"I am very sad to confirm that there have been a number of fatalities. 

"I cannot confirm the number at this time due to the size and complexity of this building. 

"It would clearly be wrong for me to speculate further. 

"Equally the cause of this fire is not known at this stage. 

"We are working very closely with our colleagues in the Metropolitan Police and the London Ambulance Service to bring this situation under control. 

"Further information will be made available shortly including advice for those concerned about those who are working here and people who live here." 

Roads in the area remain closed and there are no Hammersmith and City or Circle line services between Hammersmith and Edgware Road. 

A Metropolitan Police spokesperson said: "Police were called at 01:16hrs on Wednesday, 14 June to reports of a large fire at a block of flats in the Lancaster West Estate, W11. 

"Officers, the London Fire Brigade and the London Ambulance Service are currently at the scene. 

"An evacuation process is underway. 

"Residents continue to be evacuated from the tower block. A number of people being treated for a range of injuries. 

"The Local Authority has been informed. 

"Cordons are in place and it is advised that the estate and surrounding area is avoided." 

Ambulances were called at 1:29am, and have taken patients to a number of west London hospitals. 

Assistant Director of Operations at London Ambulance Service, Stuart Crichton, said: "We can confirm that we have taken 30 patients to five London hospitals following the incident at Lancaster West Estate, W11. 

"We have declared a major incident and continue to work closely with other emergency services at the scene. 

"We have over 20 ambulance crews at the scene as well as our hazardous area response team and trauma teams from London's air ambulance who travelled to the scene by car. 

"Our priority is to assess the level and nature of injuries and ensure those in the most need are treated first and taken to hospital."