The family of the Morrinsville toddler who died in hospital on Saturday night were known to Child Youth and Family.

"Although we have had no involvement with the toddler, her wider family is known to Child, Youth and Family," said general manager Lorraine Williams.

"My condolences are with those who loved and cared for her. We will continue to work alongside the police as they complete their investigations."

Residents near the Studholme St house in the Waikato town say they were told the toddler had brain damage when paramedics arrived on Saturday afternoon.

Police said she had serious injuries and said her death was suspicious. However, they remained cautious about labelling it a homicide.

Spokesman Andrew McAlley said there were still a number of medical tests that had to be carried out. The cause of death had not been confirmed.

Whanau still had to be contacted before the name would be released and that might not be for days.

Mr McAlley said that initial reports of brain damage were speculative and unconfirmed.

Waikato DHB spokeswoman Mary Anne Gill said hospital staff were "traumatised" by the incident.

"When it's young children it hits them quite hard," she said.

A resident who had just worked a night shift, awoke to banging on her door just after midday on Saturday. A "panicked" young man asked her to phone an ambulance and when she asked why he said "the baby's not breathing". He and a young woman took the toddler to the local medical centre, but came back to wait for paramedics when it was closed.

The toddler was flown to Waikato Hospital in a critical condition and died overnight.

Yesterday, a security guard manned the single-storey, yellow stucco home on the main street of Morrinsville, as rain poured down. Detectives and forensic experts came and went, conducting their inquiries.

Residents on both sides of the street said people "came and went" at the house and they had not known a toddler lived there. Police would not say whether the house was the 22-month-old's home.