Six people, including three children, two teenagers and an adult have died following a house fire in Neasden, north west London, the London Fire Brigade said today.
Emergency workers were called to the semi-detached property in Sonia Gardens during the early hours of this morning after a blaze took hold of the ground and first floors.
Two other people who escaped from the burning home, believed to be a man and a 16-year-old girl, were taken to hospital with burn injuries, officials said.
It is believed all the victims, which include a boy of five, are members of the same family.
The fire is being treated as unexplained, and the Metropolitan Police and LFB have begun an investigation, a police spokesman said.
Around 30 firefighters from Willesden, West Hampstead, North Kensington and Park Royal fire stations were called to the serious blaze at around 1am, fire officials said.
They were joined by officers from the Met and medics from London Ambulance Service.
The fire brigade said the blaze was under control by 2.50am.
A LFB spokesman said: "It is understood that there were six fatalities - it is thought that this may be three children, two teenagers and one adult, but we await confirmation.
"Two further people escaped from the house before firefighters arrived at the scene, both were injured and were taken to hospital by ambulance."
An LAS spokeswoman said that the two injured victims, a 55-year-old man and 16-year-old girl, were taken to Saint Mary's Hospital in Paddington.
She said: "We were called at 12.51am by the LFB to reports of a fire at Sonia Gardens. We sent the air ambulance doctor in a car, four ambulance crews and a hazardous area response team. Sadly four youngsters and an adult were dead at the scene. Our staff treated a five-year-old boy in cardiac arrest but despite extensive efforts they were unable to resuscitate him.
"We treated two further patients for burn injuries, a man, reported to be 55 and a 16-year-old female. They were both taken to St Mary's hospital as a priority."
A Met Police spokesman said the girl was understood to be in a critical condition while the man was less serious.
He added that they were awaiting official confirmation of the six deaths and that post mortem examinations would be scheduled in due course.
"We are working with the fire brigade to establish the circumstances of the fire but it is currently being treated as unexplained," he added.
Station manager Glen Gorman, who attended the scene, said: "There's no doubt, this is an absolute tragedy. My thoughts, and those of my colleagues at the London Fire Brigade, are with the friends, family and loved ones of those affected at this extremely sad and difficult time.
"We are now working with the police to ensure a full and thorough investigation is carried out."
Glen Gorman, of London Fire Brigade, speaking at the scene to BBC News, said: "Crews worked extremely hard in some very, very, difficult conditions and were able to prevent fire spreading to adjoining properties and causing further injuries or even further tragedy.
"There is a forensic examination being carried out at the moment, our specialist fire investigation unit, in conjunction with the Metropolitan Police fire investigators, will carry out a full investigation which could take a number of days to reach its conclusion."
He added: "Our sincere condolences go out to the family and the friends of the people who have been involved in such a tragic incident."
Mr Gorman said that 30 firefighters had arrived on the scene on six fire engines.
Speaking at the scene he said: "Firefighters were faced with very intense heat and smoke, it was a very difficult situation to deal with, and whilst they were dealing with that they managed to prevent the fire from spreading to the adjoining property and prevented further injury or loss of life."
Mr Gorman said London Fire Brigade could not give out details of the people who were caught in the blaze because investigations are ongoing.
He also said that although there was no indication yet of how the fire had started the fire brigade and police investigation would be "very thorough and leave no stone unturned".
The Metropolitan Police confirmed that a woman, two teenage girls and three children had died in the fire.
The adult was a 41-year-old woman, the two teenage girls were 14 and 13. The children were a nine-year-old girl and two boys aged five and two.
A spokesman for the force also confirmed that two people had been injured in the fire.
He said: "Two people have been taken to west London hospitals - a man, aged 51, and a girl aged 16 years.
"The girl is understood to be in a critical condition and the man's condition is described as stable.
"All those killed and injured are believed to be members of the same family."
A neighbour who wished to remain anonymous said: "I was in my room and the window was open.
"I heard a loud bang, it was literally like an explosion, almost like a bomb.
"I thought it was really strange and within four minutes I heard sirens and police cars and we looked out the window and the fire had literally reached the top within five minutes.
"We all went outside and we saw firemen looking out the window and shouting 'there's people in there'."
"It was horrific, my dad says he's never seen anything like it in his whole life, honestly I was so shocked."