Police investigating a fire south of Auckland in which a woman was found dead say post-mortem results show she was killed as a result of the blaze.
The 49-year-old's body was found in the gutted Pukekohe two-storey home on Tuesday.
Police say the fire appears to have started in a bedroom on the upper floor. Two other people in the house at the time managed to escape.
A man, 18, and a 16-year-old girl have appeared in court charged with arson.
Police say more serious charges are likely to be laid.
Police say the accused knew the victim, and her three sons, who were not home at the time of the fire.
They say the woman's identity cannot yet be confirmed and it will be up to the Coroner to determine an exact cause of death.