The owner of a day care where a 1-year-old boy died of fentanyl poisoning and three other children were sickened pleaded guilty Tuesday to federal charges, resolving a case that horrified New York City and underscored the scourge of the nation’s fentanyl epidemic.

Grei Mendez pleaded guilty to one count of conspiracy to distribute narcotics resulting in death and serious bodily injury, one count of possession with intent to distribute narcotics resulting in death and one count of possession with intent to distribute narcotics resulting in serious bodily injury. The three counts carry a minimum of 20 years in prison and a maximum of life in prison.

Prosecutors said the children were poisoned because Mendez, her husband and a co-conspirator chose to operate a large-scale fentanyl packaging and distribution facility inside her day care, which she ran out of a small apartment in the Bronx.

On the afternoon of Sept. 15, 2023, when 1-year-old Nicholas Dominici and another child became unresponsive, prosecutors said Mendez placed a series of phone calls: first to the community center that had referred the children to the day care, then to her husband, and then 911.

Moments after Mendez called 911, but before emergency personnel arrived, prosecutors said her husband was seen on surveillance camera rushing through the front door and then leaving out of the back of the building with two heavy bags.

Nicholas died from the fentanyl and three other children -- ranging in age from 8 months to 2 years -- were hospitalized and treated with Narcan, police said.

At the day care, authorities discovered a one-kilogram brick of fentanyl, two kilo press machines and two trap doors that revealed concealed compartments under the floor tiles of the playroom, authorities said.

Inside the traps were more than 11 kilograms of drugs, including fentanyl and heroin, as well as tools used to brand, package, distribute and traffic narcotics, the indictment said.

Federal prosecutors said they have surveillance footage and a voice message in which Mendez said that running a day care is not her "thing" in order to prove that the facility was a front for the narcotics operation.

"Grei Mendez has just admitted she conspired to maintain and distribute large quantities of dangerously toxic fentanyl in a Bronx Daycare center, a place where parents expected their children would be protected and safe," Damian Williams, U.S. attorney for the Southern District of New York, said in a statement Tuesday.

"This case has shown the senseless collateral damage caused by the fentanyl epidemic, and should remind us all that the demand for illegal narcotics so often puts innocent bystanders at risk while drug traffickers ruthlessly pursue profits," Williams added.