KEY POINTS:
The serious skull fracture sustained by a four-month-old Motueka boy was not an accident, but it was hard to determine who inflicted it, police say.
An ambulance was called to a house in Motueka, 54km northwest of Nelson, about 11pm on Labour Day after the boy's parents reported he was not responsive.
The baby was transferred to Auckland's Starship Hospital late on Tuesday afternoon.
He was improving but in a serious condition and likely to remain in hospital for at least the next few weeks, said Detective Sergeant Kevin Tiernan of Nelson CIB.
"They're definitely considered to be non-accidental injuries...(because of) the extent of damage, really. You don't just get a skull fracture from dropping a baby," he said.
There was a high possibility that the baby - who was otherwise healthy and well cared for - had suffered some sort of brain damage.
The paediatrician could not date the injury, and the boy's condition could have deteriorated slowly over the weekend so it may not have been obvious when the injury occurred.
"We've spoken to both parents now, and they've given an account for the weekend but they can't explain when or how the child may have incurred these injuries," Mr Tiernan said.
The parents had been very co-operative and were assisting police fully, he said. Police were likely to talk to them again next week.
"It's very difficult, because there were a number of adults at the house, any one of whom in isolation could have done it," Mr Tiernan said.
Police were talking to friends and family, and would re-interview a number of people.
"If we could identify who inflicted the injures, there'll definitely be charges, but it's trying to work out who's done it. Certainly at this stage we don't know who's done it."
The parents had also been caring for an extended family member's 13-month-old infant, who was now in Child, Youth and Family care, the Nelson Mail reported.
- NZPA
