Authorities say an Illinois woman charged with murder in the death of a newborn girl is likely the mother of two other infants found dead in the trunk of an impounded vehicle.

Winnebago County Coroner Sue Fiduccia also said Thursday that the babies are thought to be female and are not twins. She says their cause of death hasn't been determined yet.

The remains were found in August in a vehicle registered to 28-year-old Katie Stockton.

Stockton is charged with first-degree murder in the death of a newborn girl who was found frozen in 2004. She has pleaded not guilty. Attorneys from the Winnebago County Public Defender's office have been assigned to Stockton's case. They did not immediately return a message Friday.