A baby boy who was seriously injured in Tauranga on Sunday suffered "non-accidental" injuries, police have confirmed.
The three-week-old was hospitalised and remains on life support in Auckland's Starship Hospital.
Detective Senior Sergeant Greg Turner said the investigating team have been left "shocked" by the extent of the baby's injuries.
"Our hearts go out to this child," he said in a statement on Thursday.
"We want to assure the public that police are working extremely hard to find who is responsible and hold them to account."
A forensic examination has taken place at an address in Welcome Bay, police confirmed on Monday.
"A dedicated team of 13 investigators remains focused on bringing this matter to a conclusion and they have been working around the clock to do so," Snr Sgt Turner said.
Snr Sgt Turner has appealed for anyone who knows anything to contact Tauranga Police, "including any member of the family or wider community".