Three of the victims who died in the house fire in Hounslow are believed to be children.
Police are investigating the fire which killed five people on Sunday night and believe the victims are all members of the same family.
A spokesperson for London Fire Brigade said that they are “keeping an open mind” when it comes to the cause of the fire.
Ten fire engines and around 70 firefighters were called to the blaze on Channel Close at 10.26pm on Sunday, November 12.
The ground floor and first floors of the mid-terraced house were destroyed by the fire and part of the roof was also damaged.
Speaking at the scene, Chief Superintendent Sean Wilson of the London Fire Brigade said: “Sadly, we believe that three of those that have died were children and there is at least one other person, an adult, who remains unaccounted for.
“This is truly a terrible incident. The loss of so many lives will cause unimaginable distress to the family and friends, and the communities, of all those involved.
“I know that people across the country will be shocked and saddened by this terrible event last night.
“Everyone will want to know why this tragedy occurred and we will be working tirelessly with our colleagues in the London Fire Brigade to find those answers.
“At this time we have an open mind as to the cause of the fire and I would ask people not to add to that uncertainty by speculating.”
Mr Wilson, when asked if he could rule out fireworks as a possible cause of the fatal blaze, said: “At this stage, this is being investigated both by ourselves and specialist fire officers.
“I am not ruling anything out, I don’t think we are in a position to do that.
“We keep an open mind, it is such an early stage and there is an awful lot of work to be done.”
Five people on the first floor of the building were pronounced dead at the scene.
One man left the property before emergency crews arrived and was later taken to hospital.
His injuries are not believed to be life threatening.
One person remains unaccounted for.
The blaze was brought under control by 01.25am on Monday.
The cause of the fire is currently unknown, and a criminal investigation has been launched.
At this early stage in the investigation there have been no arrests.
Anyone with any information is asked to call police on 101 and give reference 6845/12NOV.
London Fire Commissioner Andy Roe said: “This is a terribly sad incident and the thoughts of all of us at London Fire Brigade are with the family, friends and all those affected at this difficult time.
“Staff will be in the local community today to offer support and advice where needed.
“The welfare of our staff is very important and all those involved will be offered support from our counselling and trauma service.”
Chief Superintendent Sean Wilson, responsible for policing in Hounslow, said: “My thoughts are with the loved ones of those who very sadly lost their lives in this tragic incident. I don’t underestimate the impact that this will have on the wider community and beyond.
“I understand that there will be a demand for answers and my officers are working to establish exactly what has happened.”
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