SAN DIEGO (AP) — Authorities say the remains of twin human fetuses have been found at a San Diego wastewater treatment plant and police are trying to find the mother.

Police were called to the plant on Harbor Drive on Thursday after the remains were found.

Police homicide detectives are calling the deaths suspicious although details remain under investigation.

Authorities say their main concern right now is the welfare of the mother. Police say investigators are worried that she may have had some type of medical distress while giving birth.

Police also note that California adopted the Safe Surrender Baby Law 20 years ago to prevent child abandonment. It allows newborns to be anonymously left at hospitals or fire stations.