A six-year-old girl died and four other children had to jump to safety with their mother after an arson attack on their home.
Alisha Begum was trapped in the house in Birmingham after two men threw petrol through the front door just before midnight on Friday.
Detectives are treating the girl's death as murder and linking the fire with an earlier row outside the house in the Perry Barr area of the city.
Four of the girl's siblings, who are aged from five to their late teens, and their mother, who is in her 40s, managed to leap from a first-floor window. The family were treated in hospital for minor injuries and smoke inhalation but did not require admission.
Alisha was taken to Birmingham Children's Hospital, but died on Saturday evening.
Police said two Asian men wearing dark clothes forced their way into the house at 11.45pm on Friday and threw liquid, believed to be petrol, which they then set on fire. The men, who are thought to have been accompanied by others, then fled the scene.
On discovering the blaze, the Begum family fled upstairs and leapt from a window, but Alisha became trapped and had to be rescued. Police could not confirm which room she was in or whether she was asleep at the time of the attack.
The attack happened after an earlier disturbance on Friday evening involving several people at the front of the Begum family's house, police said. The family's Vauxhall Astra, which was parked outside the house, was damaged.
Chief Superintendent Stephen Dugmore of West Midlands Police said: "We believe there is a history of some kind behind what happened.
"We know there was a disturbance outside the house the night before and I would ask people, if they know anything, to get in touch. It's a heartless crime."
A spokesman for West Midlands Police said: "The people who did this knew there were people inside which makes it particularly sad."
It is thought the children's father returned from Bangladesh this weekend, after the attack.
Neighbours said the family had been living at the address for about two years.
Forensic scientists have been examining the scene of the crime and police are looking at CCTV evidence. Up to 40 officers are working on the investigation.
House-to-house inquiries are continuing and a police incident room has been set up. Anyone with information is asked to contact detectives on 0121 322 6074 or Crimestoppers on 0800 555111.Reuse content