Police are investigating how a three-month-old from Masterton sustained what they believe to be non-accidental injuries

The baby girl remains in critical condition in Auckland's Starship Hospital, a week after police were called when she was taken to Wairarapa Hospital.

Detective Inspector Haley Ryan says someone knows what happened, and they're doing all they can to get answers for a victim who has no way of speaking up for themselves.

Ryan's encouraging anyone with information to come forward, adding silence helps no-one.