Police are still trying to establish where a dead Whanganui baby had been living.
Two-month-old Hinekawa Topia, a triplet, died in hospital on Thursday from what police say were non-accidental head injuries.
Detective Senior Sergeant Neil Forlong told Radio New Zealand's Summer Report on Monday they will speak with more witnesses, as they try to piece together what happened.
Mr Forlong said the baby's family was being very co-operative.
Hinekawa's two sisters, who are still in hospital, are doing fine and should be discharged in the next few days.
The babies and their five-year-old brother are in the custody of Child, Youth and Family.