Police say a baby boy seriously hurt last month was deliberately injured.
The 3-week-old was involved in an incident at Welcome Bay in Tauranga on 30 December.
He remains on life support at Starship Hospital in Auckland.
Police said the boy's injuries were non-accidental and have shocked the officers working on the case.
A team of 13 investigators are working around the clock to find who is responsible.
Anyone with information is asked to contact Tauranga police.