A house fire that killed a 22-month-old girl ignited during birthday celebrations for her older sister who has been left fighting for life in hospital.
Harlyn has been remembered as the "light of her parents' life" after the blaze at a Rokeby home in Hobart's eastern suburbs on Sunday morning.
Investigators have revealed the fire ignited in a lounge room during a family gathering for Harlyn's sister Jordan's fifth birthday on Monday.
Neighbours broke windows of the house to try to get people out.
"Without their assistance, this tragedy could have been even worse," Tasmania Police Inspector Andrew Keane said.
"The Rokeby community is a very tight community, always looking out for each other.
"We’ve had a lot of offers of help from people in the street already."
An online fundraising page set up by a family friend had on Monday afternoon raised more than $10,000 to help with funeral costs and rebuilding the home.
Emergency services personnel who were first on the scene have been left "devastated" but had returned to work, Insp Keane said.
"They're human beings," he said.
"They have to go home at the end of their shift to their family and their children after seeing terrible things."
Tasmania Fire Service investigator Tim McKay said the initial scene was "very difficult".
"(We) will leave no stone unturned to work out what's happened," he said.
Preliminary assessments have not determined what sparked the fire, but investigators say there were no suspicious circumstances.
Daniel Steel, the girls' uncle, told the ABC Harlyn had a "generous" smile.
"She was such a chatterbox ... she was learning everything. She was the light of her parents' life. She was the light of my life," he said.
Local mayor Brendan Blomeley said the region's council would seek to provide support.
"My thoughts and prayers are with the family and all those impacted," he said on social media.
"We are grateful for the first responders and local heroes who put their safety on the line to assist those in need."
