Investigators are working to learn more about the death of an infant in Plymouth after autopsy results came back showing meth in the baby's system.

A probable cause affidavit outlines why the mother is now in jail on two separate charges of neglect of a dependent resulting in death.

One was filed because of she originally told law enforcement about the death, and the second involves information that investigators found later.

The probable cause affidavit says when 36-year old Ashlee Rans called first responders to the Plymouth home where the baby died, she blamed herself for rolling over her baby while asleep.

However, investigators found out that wasn't the reason the baby died.

"The cause and manner of death were determined by the forensic pathologist, and he determined the infant died of acute methamphetamine intoxication, and the manner of death was homicide," Marshall County Chief Deputy Prosecutor Tami Napier said.

The autopsy happened the day after the infant died, showing both amphetamine and methamphetamine in the baby's system

The affidavit says Rans only admitted to using marijuana, and she was aware there was a possibility of transferring the drug to her child through breastfeeding. Only after the autopsy was performed did she admit to being on meth two days before the infant's death.

Napier says while both charges are still under investigation, these types of accidents can be prevented.

"Every year, we get those cases where people fall asleep with their infant in their arms in a chair or in bed or somehow end up asphyxiating an otherwise healthy child, just from unsafe practices," Napier said.

Rans is currently in custody at the Marshall County Jail. She faces between 20 and 40 years in prison if convicted on the charges.

Her initial court date has not yet been made public.