"I don't know why. I just didn't take it off of her this time," she told investigators.
>> Read more trending news
The woman woke up several hours later and noticed that the girl appeared to be half-asleep, she said. Her fiance, who was also the father of the girl, reportedly called police around 9 p.m. He stayed on the phone with emergency services while attempting to perform CPR on the infant and seemed to be "in a panic," authorities said.
Police who arrived on the scene described Sagarnaga as "lacking emotion."
The baby was pronounced dead that night.
Before the police arrived, authorities said the father told Sagarnaga to clean up around the house so that the other children, ages 1 and 2, would not be taken by the Department of Child Safety. The children were ultimately removed. The baby also appeared to be neglected, authorities said. She died in a "soiled diaper, which appeared to have been on for more than a day," and had a severe diaper rash, police said.
A day before the child's death, Sagarnaga was accused of using a bottle to hit the baby's lip and causing a laceration.