The cause of the fatal fire in Flat Bush which killed three members of the same family is officially undetermined following an investigation.
Fire investigator Phil Faidley said while the investigation team had a theory about what had caused the fire, they were not able to conclusively determine how the fire started.
Bhamini Theiventhiran, her son Bareth Kailesh and her mother Umadhevi Theiventhiran died shortly before Christmas.
They were farewelled in a funeral service at the Manukau Gardens last Thursday.
The trio died when a fire ripped through their Flat Bush home on December 22, leaving Bhamini's husband Kaileshan Thanabalasingham with burns to 40 per cent of his body and in a medically-induced coma.