NEW YORK - The call came in Friday afternoon: Three children at a tiny, ground-floor daycare centre in the Bronx in New York City could not wake up from nap time.

Emergency medical workers arrived at the six-storey brick building around 2.45pm to find a one-year-old unconscious, along with a two-year-old boy and an eight-month-old girl. The responders at once suspected drugs.

They gave the young children the overdose-reversal medication Narcan and took them away. Another two-year-old boy, who had left the daycare centre shortly after noon, was taken to a hospital after his mother noticed that he was unusually lethargic.

Nicholas Dominici, who would have turned two in November, was pronounced dead at Montefiore Medical Centre on Friday.

By early Saturday, the other three children were in critical or stable condition, and the police were questioning a person after discovering equipment typically used by drug dealers on the premises.

Nicholas’ death brought together two crises that afflict New York and the nation at large: working parents’ desperate hunt for affordable, dependable childcare and the scourge of opioids such as fentanyl, which contributed to about 75,000 overdose deaths in the United States in 2022. The Bronx has been hit particularly hard by the drug, which can kill in minute quantities.

“This crisis is real, and it is a real wake-up call for individuals who have opioids or fentanyl in their homes,” New York City Mayor Eric Adams said at a briefing just after midnight.

On Saturday, at least one person was in police custody and being questioned, according to the police.

After an autopsy on Saturday, the New York City medical examiner’s office said further examination was needed to determine Nicholas’ cause of death. The police did not name the person or people whom they had in custody on Saturday.

Mr Joseph Kenny, the police department’s chief of detectives, said at the news briefing that suspicions about opioid exposure were prompted by the children’s symptoms and by the discovery of a so-called kilo press – commonly used by drug dealers when packaging large quantities of drugs – at the daycare centre during a search.

There were 2,668 fatal overdoses in the city in 2021, reaching “unprecedented levels”, according to data released by the city in 2023.

The increase was driven by fentanyl, a synthetic opioid involved in 80 per cent of overdose deaths that year, and residents of the Bronx had the highest rate of deaths, the city found.

The daycare centre, Divino Nino, is in the 52nd Precinct in the northern portion of the Bronx, which is among the areas hardest hit by fatal overdoses.

It was not clear how the children could have come into contact with any drugs. Nearly all cases of children being exposed to opioids in the US involved the children ingesting the drug, a 2019 study in the Journal of Pediatrics found.

The study looked at more than 80,000 records of children who had been exposed to opioid-containing drugs from 2010 to 2014 and found that roughly 99 per cent of the exposures involved children ingesting the drug.

The other routes of exposure included inhalation or contact with children’s eyes, but the data in the study was largely self-reported, making it difficult to determine if those types of exposure would have been enough to sicken children.

At the midnight news conference, Dr Ashwin Vasan, commissioner of the city’s Department of Health and Mental Hygiene, said “a small child – not someone we would think would be at risk of interacting with opioids – has come into contact with a powerful substance”.

“What it tells us is that the overdose crisis affects all of us, which is why it’s an all-hands-on-deck public health moment,” he added. “Our hearts go out to the family for their loss.”

Nicholas’ father Otoniel Feliz said in an interview with WCBS-TV that the boy, the youngest of five, had been at the daycare for a single week and was just getting acclimatised. The daycare had passed its inspections and was recommended, and the family had endured a wait-list, he said in Spanish.

“The hardest thing for me is to come home and open that door and not see Nicholas saying, ‘Dad, dad,’” Mr Feliz said.

The boy’s mother, Ms Zoila Dominici, said her son was “so intelligent. He would repeat everything you would say to him. He had so much love”.

The daycare centre at 2707 Morris Avenue where Nicholas died, 800m from his home, was registered in May and had capacity for eight children aged between six weeks and 12 years, according to public records.

Calls to a number listed for the daycare centre were not immediately returned on Saturday. A woman who answered a phone for Grei F. Mendez De Ventura, a person listed as a contact for the location, said she did not wish to be interviewed.

Officials said the daycare centre had been licensed by the state’s Office of Children and Family Services after passing two inspections. A “surprise” inspection last week by the city’s health department on behalf of the state agency found no violations, Dr Vasan said.

Unannounced inspections of licensed childcare providers are standard procedure and do not necessarily indicate that a problem is suspected.

A spokesman for the state agency, Mr Solomon Syed, said he could not comment on an investigation.

Tiny daycare centres on ground floors of apartment buildings are a common sight in working-class neighbourhoods in New York, where parents struggle to earn enough to pay for care and providers try to eke out a liveable income.

Madam Anna Ortiz-Irving, 73, who lives next door to Divino Nino, said she was friendly with the mother and daughter who she said own it, and that they had worked hard for months to spruce it up, laying down new floors and putting up walls.

The windows of the daycare centre are covered with blue metal grates, a Minnie Mouse sticker adorning one window covering. Behind curtains decorated with coffee mugs, scented candles sit on the windowsills next to a collection of books.

“It is not a basement,” Madam Ortiz-Irving said. “It is a walk-in apartment. You could walk by and look right in and see how nice everything was. She always had the window open. They had gates, but you could look right in and see how beautiful it was inside.”

Madam Ortiz-Irving said that a neighbour told her that some time after 2pm, one of the women who operated the daycare centre ran outside and screamed for help because she was unable to wake the children up from a nap.

“Somebody called 911, but she was panic-stricken,” she said. “I don’t know what happened,” she added. “All I can tell you is, she and her mother are decent people.”

As the rapid spread of fentanyl has propelled a grim death toll in New York City and elsewhere, young children have not been spared.

Opioids were the leading cause of poisoning deaths in children five years old and younger from 2005 to 2018, a study in the journal Pediatrics found.

The study, published in March, looked at 731 poisoning-related deaths across 40 states. NYTIMES