York Regional Police homicide detectives are investigating, as is standard procedure for when a child under the age of five dies.
The child was from Toronto. It's not known how many children were being looked after in the house, nor is there a confirmed cause of death at this time.
Police will wait for the results of an autopsy before determining whether charges will be laid.
The Ministry of Education, which deals with unlicensed day care, is involved in the investigation.
The daycare centre has since been shut down due to numerous health infractions.
A Marketplace investigation in February found that just 20 per cent of Canadian children have access to licensed daycares.