Preliminary results from a post-mortem examination of a newborn girl found dead in Te Puke on Friday are inconclusive, police have said.
Police said the baby was born to a 17-year-old who had concealed her pregnancy and its death appeared to be the result of a "hidden pregnancyand birth".
Police will seek expert medical and legal advice to try to establish the cause of the death.
A scene examination of the rural Te Puke property where the baby was found has also been completed and and arrangements are being made to return the baby's body to family members.
Senior Sergeant Rob Glencross, the officer in charge of the investigation, said police inquiries could take several months.
He would not detail the circumstances of the death but earlier said the girl had hidden her pregnancy from her entire family.
Mr Glencross said "no medical support was sought" for the birth.
Officers were notified of the death after the baby's body was taken to Tauranga Hospital on Saturday.
Family members told them the baby had died in the early hours of Friday, soon after she was born.
Members of the baby's family, including her 17-year-old mother, were interviewed at the weekend.
Mr Glencross said the family were co-operating fully with police.
Officers had been told a "version of events" about how the baby died but he would not reveal the circumstances publicly. Asked if the death was suspicious, he said, "Absolutely."
Mr Glencross said no ambulance was called for the baby before the body was delivered to hospital. The baby's mother was not among the family members who took the body there.
Staff from the Institute of Environmental Science and Research (ESR) in Auckland were assisting police.
Detectives from the Tauranga CIB spent Saturday interviewing the family, including the mother, and Tauranga Hospital staff.
The hospital would not comment about the interviews with its staff, saying it would be inappropriate to do so while there was an ongoing police investigation.
St John confirmed no ambulance had been called for the baby.
