A neighbour of a house where a baby sustained serious non-accidental injuries says yelling had been heard coming from the house in the past.

The three-week-old boy is on life support in Starship Hospital after sustaining what police have described as serious injuries.

He was flown from Tauranga to Starship Hospital in Auckland on December 30.

All was quiet at the Arawata Ave house, in the Tauranga suburb of Welcome Bay, on Friday, but a neighbour said there had been arguments there in the past.

The neighbour, who did not want to be named, says she had seen the couple that lived there arguing outside the house on two occasions.

"Nothing too serious to raise alarm bells or call the people Police," she says.

"Pretty much just yelling."

She describes the young parents as quiet, saying they kept to themselves.

She was also unaware a baby was at the house, as she'd only seen a toddler on the property.

"We didn't even know she'd had a baby" she says.

She also revealed police forensic teams spent three days at the property and had questioned neighbours about the possibility of domestic violence at the address.

Detective senior sergeant Greg Turner, of Tauranga CIB, says the baby was seriously hurt, and on life support, but was improving.

"Police are yet to fully determine the circumstances surrounding the boy's injuries but we can confirm they are non-accidental," he said in a statement.

Greg says a team of 13 investigators are working on the case.

"We're asking anyone who has any information, including any member of the family or wider community, to please contact Tauranga Police on 07 577 4300."

-Stuff.co.nz/Benn Bathgate