A taped package containing several thousand dollars worth of fentanyl was discovered inside the New York City daycare centre where a 1-year-old child died of an opioid overdose last week, according to a court filing.

The owner of the daycare centre, however, maintained she had no knowledge of the presence of the highly potent opioid, which made three other young children ill, including an 8-month-old girl who tested positive for fentanyl use.

The drug was found underneath a mat where the children had napped, New York Police Department chief of detectives Joseph Kenny said at a news conference Monday evening.

Grei Mendez, a 36-year-old who operated the Divino Nino daycare inside a Bronx apartment, pleaded not guilty on Sunday to murder charges relating to the death of Nicholas Dominici. A man who rented a room inside the Bronx apartment, Carlisto Acevedo Brito, 41, is awaiting arraignment on the same set of charges.

Police said they recovered about one kilogram of fentanyl, along with a press device used to combine the drug with other narcotics, inside the closet of a hallway connected to the apartment. A second press was found inside the adjoining room occupied by Brito, according to a criminal complaint.

“We’re not going to allow this incident to take place and ignore this as just another day, another tragedy in the city,” New York City Mayor Eric Adams said at the news conference. “It’s not acceptable.”

An attorney for Mendez, Andres Aranda, said his client lived above the daycare centre and rented out a room to Brito, her husband’s cousin, for $200 per month.

“Apparently when the daycare was not open, people came in and out of the apartment,” Aranda said.

Friday was a “normal day” inside the daycare centre, with Mendez bringing the children upstairs, reading and cooking for them, and then putting them to sleep, he said. But when Dominici didn’t wake up from his nap, she became terrified, calling 911 and shouting for neighbours, her lawyer said.

Mendez, who also works as a home health aide, was sent to Rikers Island without bail following an arraignment on Sunday night. Brito was due to appear in court on Monday afternoon. A message left with Brito’s attorney wasn’t immediately returned.

The daycare facility opened in January of this year. It passed both of its inspections, authorities said, as well as being cleared following a surprise visit made by inspectors earlier this month.

When emergency personnel arrived at the apartment on Friday afternoon, they discovered Dominici, as well as an 8-month-old girl and a 2-year-old boy, showing signs of opioid intoxication. Medics administered Narcan, an overdose-reversing drug, to all three, helping to counter the symptoms of the 8-month-old and 2-year-old.

Dominici was pronounced dead at a hospital in the Bronx later that day.

A fourth child who had attended the daycare was taken to a hospital by her mother after showing signs of opioid exposure, including shortness of breath and unresponsiveness.

It remains unclear how the children may have been exposed to the drugs. The cause and manner of Dominici’s death are pending further study, according to the city’s medical examiner’s office.

Fentanyl, a synthetic opioid that is up to 50 times stronger than heroin, has become a primary driver of soaring overdose deaths both nationally and in New York City. Illegally made fentanyl is often added to other drugs, including heroin, cocaine and methamphetamine, to increase its potency.

Unintentional drug overdoses among children are also on the rise, with opioids the most common substance contributing to fatal poisoning of kids.

In the overwhelming majority of cases, children were found to have orally ingested the substance, rather than touching it or inhaling particles of it present in the air, according to a 2019 study published in the Journal of Pediatrics.