The owner of a Kingsbridge day care center where a 1-year-old child died after being exposed to fentanyl took steps to cover up her involvement in a sprawling drug operation, even as medics rushed to treat several children in her care who were poisoned by the opioid, federal prosecutors said.

The day care owner, Grei Mendez, and a man who rented a room from her, Carlisto Acevedo Brito, were hit with new federal narcotics conspiracy charges Tuesday. They were previously charged in state court with murder of “depraved indifference” in the death of 1-year-old Nicholas Dominici.

Officials say they discovered a kilogram of fentanyl stored on top of playmats used by children who attended the Bronx day care center, as well as devices for packing and mixing narcotics.

The fentanyl is believed to have sickened four children, including Dominici, who died Friday afternoon. Three others — ranging in age from 8 months to 2 years old — were hospitalized.

“The defendants poisoned four babies and killed one of them because they were running a drug operation from a day care center,” Manhattan U.S. Attorney Damien Williams said at a news conference.

On Friday afternoon, Mendez, 36, discovered the young children were not waking up from nap time. She then made three calls, including two to her husband, before dialing 911, the criminal complaint alleged.

Surveillance footage showed him entering the Bronx apartment and whisking at least two full shopping bags out of the building through a back alley. Minutes later, emergency medical personnel arrived to find the children showing signs of opioid intoxication.

The phone calls, along with the apparent deletion of thousands of texts between Mendez and her husband, suggested an effort to cover up the narcotics operation inside the apartment, federal prosecutors alleged.

Williams said authorities were still seeking Mendez’s husband as of Tuesday afternoon. He was not named by either state or federal court filings.

Brito, a 41-year-old tenant of the apartment and a cousin to Mendez’s husband, was charged alongside Mendez for his alleged role in the drug operations. New York City police said they recovered a kilogram press device inside the closet of an adjoining room occupied by Brito.

Both Mendez and Brito have denied knowing anything about drugs in the day care center. An attorney for Mendez, Andres Aranda, said his client was “terrified” upon discovering the unresponsive children and acted immediately to get them care.

A message left with Brito’s attorney wasn’t immediately returned.

The day care facility opened in January of this year. It passed both of its inspections, authorities said, including a surprise visit made by inspectors on Sept. 6.

New York City, like much of the country, has seen rising levels of opioid-related deaths, with the vast majority of fatalities now attributed to fentanyl, a synthetic opioid that can be more than 50 times stronger than heroin.

Williams said the news of Dominci’s death had “shocked the conscience of a city already reeling from the devastating effects of the fentanyl crisis.”

At an unrelated press conference on Tuesday, New York City Mayor Eric Adams said the incident should serve as an “indictment on our society.”

“I don’t know what’s wrong with us,” he added. “We had fentanyl in a day care center.”