Neighbours have told of how they saw an "unusual amount of smoke" and "lots of fireworks" around the same time as a fatal house fire in Hounslow.
Five members of a family, including three children, have died following the blaze in Channel Close at 10.26pm on Sunday, November 12.
Ten fire engines and around 70 firefighters were called to the fire.
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 with non-life-threatening injuries. One person remained unaccounted for.
The Met said the cause of the fire was under investigation, but that no arrests had been made.
Speaking at a press conference at the scene, Chief Superintendent Sean 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.”
Nick Marbrow, who lives on Sutton Road, with a view towards the burned-out house from his home, said he noticed an “unusual amount of smoke” on Sunday evening.
He said: “When I went to bed last night, I could see a lot of smoke.
“I could see an unusual amount of smoke, but then it is Diwali, there were fireworks going off.
“It’s very unusual for this area, it’s safe around here.”
Ashish Sosniah, who was passing the street on his way to temple, said he saw fireworks going off “for an hour” between 8pm and 9pm.
He said: “There were lots of fireworks going off for Diwali. I could see white smoke.”
Mr Sosniah said that when he next passed at around 11.30pm there were emergency services at the scene.
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.”
The ground floor and first floors of the mid-terraced house were destroyed by the fire and part of the roof was also damaged.
Nearby homes were evacuated during the blaze, which was brought under control by 1.25am on Monday.
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