Police want to speak to anyone who knew the toddler killed in Auckland last week and his mother when they lived in Tauranga.
A homicide investigation was launched after James Lawrence died at a home in the Auckland suburb of Orakei on 14 November.
The two-year-old had suffered blunt force trauma to his stomach which severely damaged his internal organs.
Police say the toddler and his mother moved to Orakei from Tauranga around July.
No one has been arrested in relation to the boy's death.
Police understand four adults were present when he died.
They say some of them are being uncooperative.
Meanwhile, police are still awaiting post mortem results following the death of a one-year-old child in Otahuhu earlier this month.