The owners of a New York City daycare centre where a toddler died and three others made ill by opioid exposure last week were hiding bags of fentanyl beneath a trap door in the children’s play area, police say.

Detectives were searching the centre in a Bronx apartment on Thursday when they found the narcotics and other paraphernalia concealed by plywood and tile flooring. Photos shared by police show bags full of powder inside the “trap floor”, a few steps away from a shelf of children’s toys.

The discovery came nearly a week after four young children attending the daycare were treated for opioid poisoning. Exposure to fentanyl is believed to have caused the death of 1-year-old Nicholas Dominici.

The daycare operator, Grei Mendez, and a tenant of the building, Carlisto Acevedo Brito, have been charged with murder of “depraved indifference” in the boy’s death. Authorities are still seeking a third individual, Mendez’s husband and a cousin of Brito.

Police say the owners of the daycare centre where a toddler died and three others were sickened were hiding bags of fentanyl under plywood and tile flooring. Photo / AP

Before finding the drugs under the trap door, police had already announced the discovery of a kilogram of fentanyl stored near mats the children used for sleeping, along with multiple devices used by traffickers for mixing drugs and pressing them into bricks.

Federal prosecutors say Mendez, 36, took steps to cover up the drug operation last week, shortly after realising that some of the children in her care were not waking up from their naps.

Before alerting first responders, she called her husband, authorities said. He was seen on surveillance footage entering the building moments later, then leaving through a back alley with multiple shopping bags.

“All of that happened while the children, the babies, were suffering from effects of fentanyl poisoning and in desperate need of help,” Manhattan US Attorney Damien Williams said at a press conference this week.

During a federal court appearance in Manhattan, an attorney for Mendez said she did not know about the drug operation, while suggesting that her husband was responsible.

• US daycare owner arrested after toddler dies, others exposed to opioids
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Brito, 41, did not speak during his court appearance. Inquiries to his attorney were not returned.

Both face up to life in prison if convicted on federal charges of possession with intent to distribute narcotics resulting in death and one count of conspiracy. They were also charged in state court with murder, manslaughter and assault.