Antwonetta Jones was alone in her Slidell apartment Sunday as she gave birth to the baby girl she had kept secret from friends and family for nine months. Two days later, the 22-year-old woman was in jail, facing a count of second-degree murder in the newborn’s death.

Jones told police it was fear of discovery that led her to put the infant in a cardboard box, tape the box shut and put it by the apartment complex’s trash compactor.

Preliminary autopsy results show that the 6-pound, 4-ounce child with black hair lived between four and 12 hours after she was born, according to Dr. Charles Preston, the St. Tammany Parish coroner.

Jones was booked after she confessed to her mother, who in turn called police, Slidell Police Chief Randy Smith said.

Jones then told detectives that she gave birth to the child in a full bathtub. Hours later, after the child coughed and stopped breathing, she said, she panicked and boxed her up. She took the box outside and put it by the trash compactor.

The baby’s body showed no outward signs of trauma, Preston said.

The body likely would never have been discovered if an apartment complex maintenance worker hadn’t seen the box and wondered what was inside, Smith said. The worker — unnamed by police — noticed the box when he went out to the compactor about 9:15 a.m. Monday to turn it on.

Smith described the box as a speaker box and said it had been taped shut. The maintenance worker opened it to see if there was anything of value inside, Smith said.

The grisly discovery sparked a massive police investigation Monday as Slidell detectives canvassed the gated Canterbury House Apartments complex adjacent to Salmen High School. During that initial canvass, officers knocked on every door in the complex but did not speak to Jones, a spokesman said.

Meanwhile, the body had been taken by the Coroner’s Office, which began to try to identify the child and the cause of death.

It appeared that no medical personnel had assisted in the baby’s delivery. The umbilical cord, which was still attached, was much longer than it would have been had the baby been born in the hospital, Preston said. The baby’s lungs had not been suctioned, as would happen in a hospital birth, he said.

The autopsy showed that the baby girl — known at that point simply as STO 087115 — had breathed on her own, however, indicating that she had been alive after birth.

“She was a beautiful baby girl,” Preston said. The girl had been carried to full term and had no signs of trauma. She had been cleaned after birth and appeared to have been in good health, he said.

With proper medical care, “I think that baby would have survived,” Preston said.

Nevertheless, the manner and cause of death have not been determined, as several tests remain to be done, Preston said. The baby had a spot of blood and feces on her leg, but none of that was on the box, leading Preston to say it was unlikely the baby had moved after being put in the box.

Late Monday night, Jones may have been overcome by remorse, Smith said, and she told her mother, with whom she lived, what had happened. Her mother called police, providing a crucial break in a case that to that point had made little progress.

Smith called the case tragic.

“It is very disturbing to me that this young lady felt as though she had no other options available,” he said.

Smith pointed out that the state’s “safe haven” law allows new mothers to leave their babies at places such as emergency rooms, police stations and fire departments, with no questions asked.

“We have to do a better job of educating mothers-to-be that Louisiana is a ‘safe haven’ state,” Smith said.

Jones has been booked under a provision of the second-degree murder statute that says that even if a person had no intention of doing great bodily harm, refusal to provide medical care to a child qualifies as second-degree murder.

She is being held at the Slidell City Jail but will be transferred to the St. Tammany Parish Jail.

Follow Sara Pagones, @spagonesadvocat, and Faimon A. Roberts III, @faimon, on Twitter.