A day care operator and her tenant are now facing federal charges after the death of a 1-year old boy who was exposed to fentanyl at the New York City facility.

Day care operator Grei Mendez and tenant Carlisto Acevedo Brito are charged with narcotics possession with intent to distribute resulting in death and conspiracy to distribute narcotics resulting in death, according to federal prosecutors.

Mendez and Brito were initially arrested on state charges, including murder, manslaughter and assault, following the "reckless, depraved" death of 1-year-old Nicholas Dominici, prosecutors said.

Three other young children were hospitalized and treated with Narcan and are now recovering following the Friday incident in the Bronx, police said.

Mendez and Brito were arraigned on the state charges Sunday night and held without bail.

Mendez’s attorney said she was unaware drugs were being stored in her day care by Brito, her husband's cousin, to whom she was renting a room for $200 a week.

This is a developing story. Please check back for updates.