MINNEAPOLIS — Prosecutors charged a 25-year-old Minnesota woman with second-degree murder in her infant son’s 2009 death, saying she recently admitted to holding a blanket over his mouth until he stopped breathing.

Ashleigh Jennifer Casey told a St. Louis Park police investigator during a recent interview that she inadvertently killed her 3-month-old son, Alexander. The investigator was interviewing Casey several days after her 8-month-old daughter stopped breathing but was resuscitated during one of several recent hospital visits, Hennepin County prosecutors contend.

Casey made her first court appearance Friday, the county attorney’s office said Tuesday.

The case may involve a mental illness that causes parents to harm their children in an effort to seek attention.

St. Louis Park police were called March 12, 2009, on a report of a baby not breathing. Police found Casey’s 3-month-old son lying on the basement floor. After attempts to revive him, he was pronounced dead at the scene.

Casey allegedly told police her son had undergone bowel surgery less than a week earlier, and that she had taken him to a hospital earlier on the day he died because he had been crying and fussing.

Emergency room doctors found nothing wrong, and she returned home and watched television with her son lying in bed next to her. When the show ended, she realized the baby wasn’t breathing and ran into the basement to get help from other family members, who called 911, according to the complaint.

Investigators also learned that on March 3, 2009, the baby stopped breathing and Casey’s grandmother, a registered nurse, was able to revive him. Doctors could find no medical reason for him to stop breathing. An autopsy listed his cause of death as undetermined.

The St. Louis Park police investigator learned May 23 that Casey had taken her 8-month-old daughter to the Mille Lacs County hospital several times of late and that doctors couldn’t find anything wrong with the girl.

Casey then took her baby to the University of Minnesota Children’s Hospital for tests. At about 3 a.m. on May 17, Casey alerted a nurse that her daughter wasn’t breathing. The nurse performed CPR and the girl quickly regained consciousness and was sitting up and smiling. The girl’s doctor thought Casey might be involved, the charges said.

In an interview with a child protection investigator in Mille Lacs County, Casey asked numerous questions about Munchausen by Proxy Syndrome, a mental illness in which caregivers exaggerate a child’s symptoms or cause medical problems for a child in order to get attention.

In a recent interview, Casey told the St. Louis Park police investigator she held a blanket over Alexander’s mouth until he stopped breathing in 2009 and after trying to resuscitate him, ran downstairs for help. Prosecutors contend that Casey said she didn’t mean to hurt the baby and thought he would start breathing again, as he had in the past.

Casey remains in the Hennepin County jail with bail set at $500,000. Her next hearing is scheduled for Aug. 9. Her daughter is now in the care of Mille Lacs County child protection officials.

Casey’s attorney didn’t immediately respond to a phone message for comment after business hours Tuesday evening.