Investigators say the Hamilton mother charged with killing her 5-week-old son and putting the body in a garbage can murdered the child to cover up who fathered the baby.

A grand jury has indicted Asuncion Avila-Villa, 26, for unlawful sexual conduct with a minor. According to the indictment, the father is under the age of 16.

Villa is also charged with aggravated murder, tampering with evidence and gross abuse of a corpse.

Investigators say Villa killed her 35-day-old son named Israel Santos, then put his body inside a plastic bag in the trash behind her apartment on Shuler Avenue.

Authorities say they started looking for the baby after Villa called them on August 24 and tried to cover up what happened.

Villa told the 911 dispatcher: "I was just calling ‘cause ... one of my ex boyfriends came to pick up one of my sons ... He said he was going to take him. He hasn't come back yet."

Detectives worked the case all night before they found the baby in the garbage can on August 25.

The Butler County Coroner says the boy suffered from skull fractures as well as a broken arm.

Villa also has three other children.

She remains behind bars at the Butler County Jail on a $1 million bond. She is scheduled to appear in court later this week.