Investigators were yesterday examining whether the fire, which gutted Aroen and Seema Kishen’s house during the Hindu festival, was caused by sparks.
Witnesses revealed that the couple were inside the two-storey terrace home with their young family when it was destroyed by flames in the early hours.
One horrified onlooker said they heard the distraught father screaming: “My kids, my kids.”
Police later confirmed that two adults and three children from the same family were killed in the tragedy in Hounslow, west London.
The victims were pronounced dead at the scene after the blaze was brought under control by a 70-strong team of firefighters.
Another person was unaccounted for and a man escaped the inferno and was later treated in hospital for injuries that are not life-threatening.
Chief Superintendent Sean Wilson, of the Metropolitan Police, said his officers and London Fire Brigade were investigating fireworks as a possible cause.
He 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.
“Despite the life-saving efforts of all those attending, I am very sorry to inform you all that five people have lost their lives in this fire. Sadly, at least three of those were children. I know that people across the country will be shocked and saddened by these events.”
The tragedy unfolded late on Sunday night after an evening of fireworks for the annual festival of lights marked by Hindus.
Neighbour Felicia Matei, 29, said: “We saw the man who lived there with his wife and children. My daughter used to play with his daughter. He was screaming something like, ‘My kids, my kids’. It was a big fire. I screamed to my family and said we need to run away.”
Inder Kondal, 48, whose home has a view of the property destroyed, said the flames spread within 90 seconds.
He added: “What we saw was pretty crazy. We could hear people screaming and stuff. It was horrific. The fireworks going on were crazy. It was horrendous.
“My 12-year-old daughter was in the garden and saw the flames. It’s so sad. Within a minute, the fire had gone all the way through. One and a half minutes in, it was in through the back. It was instant.”