Investigators have begun removing bodies from the charred wreckage of the Russell Island home, in which 34-year-old Wayne Godinet and his five sons perished early on Sunday.
The children's 28-year-old mother Samantha Stephenson survived the inferno, managing to escape the two-storey home as it was engulfed in flames about 6am.
Detective Superintendent Andrew Massingham said some elements of the tragedy required closer scrutiny and investigators were "keeping an open mind" as to the cause.
"No determination has been made at this stage as to whether this fire is suspicious or not," he told reporters on Monday.
Det Supt Massingham said officers had previously been called to the house and Mr Godinet was known to police but he gave no further details.
Previous calls to the address were under review, he said.
Police said a 21-year-old woman also escaped the house and they were hopeful of interviewing her and Ms Stephenson on Monday.
Emergency crews found the women outside suffering smoke inhalation.
Witnesses said Ms Stephenson was screaming for help, telling first responders her family was trapped inside the burning home.
The blaze spread to two other properties that were saved by firefighters.
Several neighbourss were treated for smoke inhalation and minor burns.
Three people in total were taken to hospitals on the mainland, including Ms Stephenson.
Investigators found the bodies of Mr Godinet and the five boys - aged 11, 10, twin four-year-olds and a three-year-old - inside the burnt-out home late on Sunday.
Police have cordoned off the scene and locals have paid their respects by placing flowers, candles and stuffed toys nearby and at the entrance to the island's state school.
At least one body has been recovered from the ruined house.
One neighbour who asked not to be identified said he was fast asleep when another banged on his door telling him to call the fire brigade.
"That was the first I knew of it, I came outside and the place was ablaze," he told AAP.
The fire seemed to engulf the home in minutes, flames leaping as high as the trees as the house was razed to the ground.
"It went up really quick. Iv'e never seen anything burn that quick."
The resident said he saw the boys' distraught mother collapse on the ground.
"She was screaming and yelling. She was devastated but there was nothing that anyone could do."
The tragedy has rocked the small, close-knit community, which lies between mainland Queensland and North Stradbroke Island.
Taxi driver Angela Dowson said everyone wanted answers.
"We just want to know how something like this could happen," she said.
"The whole island is shell-shocked."
A day after Premier Annastacia Palazczuk offered her condolences, LNP leader David Crisafulli visited to pay his respects.
Redland City mayor Karen Williams said the Moreton Bay islands were in mourning but had a strong sense of community.
"This sort of grief will resonate right across not just this island but all our southern Moreton Bay islands and our city," she told ABC Radio.
The Bay Islands Memorial Gardens and Sel Outridge Park on the mainland are open for people to pay tribute.
Local authorities are setting up a fundraising account through the local registered charitable trust, The Redland Foundation.
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