A baby suffered nine fractures, including to her ribcage, ankle and arm, police have revealed.
Detective Senior Sergeant Steve Wescott said last Thursday police were notified that the three-month-old had been brought to hospital by her family in Hutt Valley on June 14.
"The baby girl had a broken arm, which appeared an unusual injury for such a young baby. Further examination has taken place at the hospital, which has identified multiple further fractures throughout the baby's upper and lower body.
"Police are investigating the circumstances of how these fractures and injuries have occurred. We do not believe the injuries could have been sustained accidentally."
Wescott some of the injuries happened at different times.
"Police are working tirelessly to find the truth about how the injuries were sustained."
The baby's condition was improving, Wescott said, but police were continuing to appeal for anyone who knows anything to come forward.
Contact police via 105, quoting file number 250614/8509.
Information could also be provided anonymously through Crime Stoppers by phoning 0800 555 111.
