Police have been called on several occasions to the house in which a 15-month-old received serious head injuries, the Herald has learned.
Medical experts say the baby boy will probably be left blind and have permanent brain damage by what they believe are non-accidental injuries.
Police said last night they would look at previous dealings they had had with a family at the Cobham Rd house in Kerikeri. Cobham Rd is where murdered teen Liberty Templeman's body was found last month.
Neighbours said they often saw police at the house after loud, all-night parties.
Far North area commander Inspector Chris Scahill said he did not know at this stage if the boy's parents were known to police, but establishing this would be part of the investigation.
Officers had not previously been called over incidents involving the boy, he said.
Police yesterday spoke to the baby's 21-year-old mother and other relatives at the boy's hospital bedside.
They will assess today who they need to re-interview.
They are also appealing to the public for information.
"We don't know at this stage who is going to be relevant," Mr Scahill said. "That will come to light as the inquiry progresses as to who we need to speak to."
Police conducted a scene examination yesterday at Cobham Rd, where the boy lives with his mother, her partner and at least one other person.
The boy's birth father was "not in the picture", police said.
"We're doing an examination of the home address to establish that that is actually the scene," Mr Scahill said.
The baby was in intensive care at Auckland's Starship hospital last night after having urgent neurosurgery on Friday to relieve the swelling on his brain.
He was taken to Bay of Islands Hospital in Kawakawa by his mother before being flown to Starship.
The hospital advised Child, Youth and Family of the child's injuries immediately and police were told on Saturday.
CYF took legal custody of the baby last night.
CYF head Ray Smith said: "At times like these everyone questions how this could have happened, and my sympathy goes out to the extended family.
"While there is little we can say as the matter is under police investigation I can confirm that the child is now in a safe and secure environment."
A neighbour told the Herald several young people lived at the property and he had seen police there before.
"They're always having parties. There's always loud music ... I didn't even know there was a baby there."
He said three police cars were at the property yesterday, and officers were walking around in white overalls.
Mr Scahill said it was too early to comment on what they found at the house.
The boy's mother was not thought to have any other children.
Mr Scahill said the fact that the boy was still alive two days after being admitted to hospital was cause for hope in terms of his survival.
"I would imagine, should he survive... there will be some permanent damage."
The case comes after the Herald ran a series investigating child abuse in New Zealand.
The Our Lost Children series spurred businesses and individuals to donate to groups trying to prevent child abuse and help its victims.
Starship hospital pediatrician Dr Patrick Kelly, who has given evidence in many child abuse cases, said at the time that about one in five babies with serious head injuries died.
Of the 80 per cent who did not die, he estimated about a third would have permanent, severe damage.
Another third would suffer moderate damage.
At Starship, hospital, where many of the most seriously injured children are treated, 86 children were treated between 2001 and 2007 for non-accidental head injuries.
About 45 new cases of child abuse come to the attention of social workers at CYF every day.