The children, who were aged between 1 and 15, were unable to escape the intense blaze which also left their parents and a 19-year-old sibling with serious burns.
Counties Manukau chief fire officer Larry Cocker said the fire started about 12.45am after hot oil that was used to cook chips on the stove ignited.
The flames moved to the ceiling and quickly spread throughout the Mangere home.
Mr Cocker said there were no working smoke alarms - something that would have given the family early warning of the fire, and undoubtedly saved lives.
Instead, two families are now grieving for the children and maintaining a bedside vigil for the injured at Middlemore Hospital.
Eight people were living in the home and another two in a sleepout at the back of the house.
It is understood Misi Sau (50) and his 39-year-old wife Fetu tried desperately to get all of the children and grandchild out of the Nicola Pl home but the flames were too intense.
Mrs Sau's 15-year-old daughter Brenda, and her 1-year-old grandson, Tyreece both died inside, as did Mr Sau's two daughters 11-year-old Taua and 7-year-old Mia.
Two of the girls were found in the living room, while the third was in the hallway near the front door.
The baby was near his cot in his bedroom.
A group of teenagers who noticed the smoke while driving down the road were among the first on the scene.
One of them, Gardenia Latham (14), described how they used a bat to try to smash their way into the house.
"A lady came out nude and . . . she was just going really crazy saying 'my baby Tyreece, my baby Tyreece'. Our friends were going to go inside to get it, but the fire was just unbelievable."
Gardenia's friend Dallas Pakeho (15), helped a teenage girl who was bleeding from the arm while another friend tended to the badly burnt 19-year-old with learning disabilities who was "pulling his skin off".
Another person who arrived quickly on the scene lived around the corner in Friesan Dr.
He said he woke to the sound of screaming for help and ran to find Mr Sau partially through a window.
He pulled Mr Sau to safety, but he was badly injured with burns to his back and bad cuts to his head, arm and ankle.
The man, who did not want to be identified, said the fire was too intense for him to help rescue the children.
"The mother said the kids were in there, so I tried to do something, but the fire was too strong."
Mr Sau is now in a critical condition at Middlemore with burns to 85% of his body.
Mrs Sau is in the burns unit in a serious condition.
Speaking from the hospital, Mrs Sau's brother George Iuta said his sister was in "total shock" over the loss of "her baby Brenda".
"She said `I can't believe it, I just can't think'."
Mrs Sau had also told him: "We could hear Brenda screaming she can't get out".
Mr Iuta said Tyreece's 18-year-old mother Fa'afetai was also distraught.
"She's just besides herself. We know she's trying to be strong, but she's not coping."
Brenda's father Maa Simati - Mrs Sau's ex-husband - said the last time he saw his daughter and grandson Tyreece was at Christmas.
"I played around with my grandson. He laughed with my daughter Brenda and was joking. He laughed and we had a good feed and talk. It's very sad."
Brenda's uncle, Meki Tapu, said he was called early yesterday morning after his brother Mr Simati received the tragic news from police.
"I was pretty shocked, especially because all the kids were with him at Christmas".
As the two men watched fire investigators sift through the debris at the scene yesterday morning they struggled to comprehend what had happened.
