ELK RIVER, Minn. (AP) — A woman who left her newborn baby in a box on the side of a Minnesota road 35 years ago won’t be charged, authorities said.

Sherburne County Attorney Kathleen Heaney closed the case earlier this month because the statute of limitations to file charges had run out, the Sherburne County Sheriff’s Office said Thursday in a news release.

A passerby found the baby’s body on April 23, 1989, in Santiago Township but investigators at the time weren’t able to identify the newborn or her parents, leaving the case unsolved, the sheriff’s office noted.

Last year, county authorities tried again with new techniques and help from state and federal investigators. A DNA match identified the mother, now 56, who told investigators she had kept her pregnancy and the birth from her family. She said the baby, a girl, was not alive when she was born, “and in a state of panic she did not know how to handle the situation,” the sheriff’s office said.

An autopsy conducted in 1989 and a subsequent review last year failed to definitively determine whether the baby was born alive, but two pathologists thought the child probably was stillborn, the sheriff’s office said.

The county coroner’s office buried the baby in 1989, but the sheriff’s office said it has been unable to find records of where.