A post-mortem will take place this morning following the suspicious death of a woman in a Hamilton house fire on Wednesday.
Police are treating her death as a homicide.
Nine people, including two young children, were in the state house on Holland Road in Fairfield when it caught fire. Adults escaping from the fire rescued the children, aged four and one, from the flaming property. Four people were taken to Waikato Hospital for treatment, including the children
The fire service said it was small fire and was extinguished with just a hose.
"The forensic evidence gathered during the post-mortem will assist in determining the direction of the investigation," Detective Senior Sergeant Nigel Keall said.
"The scene examination of the Holland Road property is expected to continue for several days and police are being assisted in their investigation by ESR forensic experts and Fire Service fire investigators."
Keall said one of the adults initially exited the home when the fire started "but then bravely returned to try and fight the fire".
"We know that one man managed to pull a four-year-old child from a lounge window and then re-entered the house to successfully rescue the baby," he said.
"Had it not been for this person's actions we would be investigating a far greater tragedy."
Approximately 30 police staff are working on the investigation.
And police are now investigating whether a second arson in the city yesterday afternoon is connected but say there's no evidence linking the two yet.