A woman is dead and two children are in a serious condition following the fire at a Callender Terrace three-bedroom home just after midnight.
Senior Sergeant Alasdair MacMillan said three adults and three children were in the house at the time of the fire.
Emergency services found a young girl and woman in the same bedroom, both unconscious, and were able to resuscitate the girl but could not save the woman, he said.
Two neighbours rescued another child from a bedroom after smashing a window at the rear of the house.
"There is little doubt if it were not for the valiant actions of the neighbours, emergency services, and the police that further loss of life would have occurred," Mr MacMillan said.
The young girl was airlifted to Wellington Hospital and the other child, who was rescued by neighbours, was taken by ambulance to hospital.
Both the children were in Wellington Hospital's intensive care unit in a serious condition, Mr MacMillan said.
Two adults and the baby were treated at the scene for smoke inhalation.
A 54-year-old man, one of the neighbour's who smashed a window, was treated for a serious cut to his hand.
Central Fire Communications shift manager Chris Dalton earlier told NZPA the house had one working smoke alarm.
The Fire Service and police will investigate the cause of the fire.
