Police in Waikato say it will be several days before tests can establish exactly how a child died during the weekend.
The girl, aged 22 months, from Morrinsville was taken to Waikato hospital on Saturday afternoon with serious injuries and she died that night.
A post mortem was performed in Auckland on Sunday but further tests are needed.
Police say they are working to ensure all relatives have been infromed before naming the girl. Her death has been referred to the coroner.