On March 29, 17-month-old Sadie-Leigh Gardner was critically injured in Tauranga and died at Starship Hospital.
Officers were called to a Maungatapu property on March 27 at 4.30pm after reports a child had been injured.
The child was admitted to Tauranga Hospital then transferred to Starship Hospital in a critical condition.
On March 21, 2-year-old girl Nevaeh Jahkaya Whatukura Ager was found dead on tidal flats in the close-knit town of Little Waihi after police were initially called to the area because of "reports of a public disorder".
Police are currently conducting a homicide investigation into the girl's death after receiving results of an autopsy on her body.
On December 30, a 3-week-old baby boy suffered serious injuries in Welcome Bay.
Detectives involved in the investigation confirmed on January 3 the injuries were not the result of an accident.
Police were notified after the baby was taken to Tauranga Hospital. He was then flown to Starship Hospital in Auckland.
• Anyone with information that could help the investigations can call Tauranga Police on 07 577 4300 or Crimestoppers anonymously on 0800 555 111.