Days after a 1-year-old died and three children exposed to drugs at a Bronx day care site were hospitalized, investigators uncovered a trap door under a play area that was concealing fentanyl, other narcotics and drug paraphernalia.

The police had already discovered a kilogram of fentanyl near nap mats at Divino Niño on Morris Avenue, but the new search was triggered by a tip that more drugs had been hidden, Lieutenant John Russo said on Thursday. A neighbor had said last week that the owners of the facility had spent months sprucing it up — including laying down new floors.