Authorities investigating a teacher's aide accused of trying to drown her newborn girl in a toilet have found the decomposed remains of another infant at her southern Illinois home.

The remains apparently had been at Elyse Mamino's home in the St. Louis suburb of Belleville for more than a year, Belleville police Capt. Don Sax said Monday. He declined to comment further pending the investigation's completion and a review by St. Clair County prosecutors. No charges in the child's death had been filed as of Monday.

Mamino, 23, was arrested last week and charged with attempted first-degree murder. Authorities allege that in November, she was at a house party in nearby Columbia when she gave birth in a bathroom and tried to drown the baby.

Someone at the party called police, first reporting the infant as dead, Columbia police Chief Joe Edwards said. But emergency responders, with help from a bystander, managed to revive the girl by the time she arrived at the hospital, Edwards said.

The baby, now in a relative's care, was hospitalized for about two weeks. Edwards said it is unclear whether she suffered brain damage.

Mamino remained jailed Monday on $250,000 bond, and it was not immediately clear whether she had an attorney. She worked as a teacher's aide in Belleville for autistic children, Edwards said.

Edwards called the case "very disturbing," in part because state child-welfare officials let Mamino keep custody of her surviving girl from the time the baby was released from the hospital in December until Mamino's arrest last week.

The child remained in Mamino's custody despite investigators "airing concerns" that the mother perhaps tried to kill the girl, Edwards said.

Illinois Department of Children and Family Services spokesman Kendall Marlowe refused to discuss those claims, calling them a matter of pending investigation.

Edwards said authorities needed until last week to arrest Mamino because of the time it took to interview witnesses and get lab results.