After fentanyl sickened three toddlers and killed a fourth at the Divino Niño day care, its proprietor, Grei Mendez, professed to be caught up in a bewildering catastrophe.

She told investigators at a police precinct in 2023 that she had no idea how narcotics had gotten into the day care, which she ran out of a Bronx apartment, according to court documents. She denied that contraband there belonged to her or her husband, who had fled while a 22-month-old, Nicholas Feliz Dominici, lay dying.

But even as she called herself blameless, federal prosecutors said, Ms. Mendez destroyed evidence contradicting her claims. Inside the precinct, she deleted tens of thousands of text and voice messages from her phone, prosecutors wrote, including some in which she and her husband, Felix Herrera Garcia, discussed trafficking drugs.

On Monday, in Federal District Court in Manhattan, Ms. Mendez, 37, was sentenced to 45 years in prison after having pleaded guilty late last year to possessing and conspiring to distribute narcotics resulting in serious injury and death.

While handing down the sentence, Judge Jed S. Rakoff said that in not acting promptly to help the poisoned children, Ms. Mendez had put her own fear of getting in trouble “above the opportunity to save a life.”

The poisoning of the four children, who ranged in age from eight months to just over two years, prompted grief and outrage, with parents and government officials demanding to know how a child care facility could have doubled as a stash house.