A couple are mourning the loss of their second child within six months.
Three-year-old Lucy Dunford was airlifted 13 miles to hospital after being found unconscious in her bedroom at the family's end-of-terrace house.
Despite attempts to revive her, doctors pronounced her dead shortly after she was admitted to the Conquest Hospital, Hastings, on Monday.
It is a second tragedy for parents Lesley King and Wayne Dunford.
Their seven-month-old son Harley died in August from natural causes.
The funeral was held in Camber on September 15 and Harley was buried at Rye Cemetery. His parents make a daily pilgrimage there.
Motoring enthusiast Mr Dunford, who named Harley after Harley-Davidson motorbikes, heard Lucy had been taken ill on his first day as an engineer at a company in Beckley, near Rye.
Sussex Police would not say how Lucy died or whether her death was being treated as suspicious.
A Home Office paediatric pathologist travelled from London yesterday to conduct a post-mortem examination.
A police spokesman said it was inconclusive and further tests were being carried out today to determine the cause of death.
Lucy's parents have lived in Pelwood Road, a cul-de-sac in Camber, near Rye, for about a year and have another daughter, Leah, two.
Family friend Bruce Martin, 74, said: "It's tragic. Only a few days ago Lucy, her sister and their parents were playing happily in the snow.
"Lucy was a really happy child and it is awful to hear she is no longer here."
Police cordoned off the home and stood guard outside as officers conducted house-to-house inquiries on Monday night and yesterday.
A Sussex Ambulance NHS Trust spokesman said Lucy was "in a bad way" when paramedics arrived at the house at 3.20pm..
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