The baby girl, believed to be around 1 year old, was found Monday around 10:37 a.m. in the 10300 block of Alondra Boulevard.
She was found in a car seat partially wrapped in a blanket, on the ground to the rear of a dumpster in the parking lot of the Funeraria del Angel mortuary.
The mortuary is on Alondra Boulevard, across the street from Bellflower Middle/High School.
Detectives said they were not sure how long the infant's body has been in the parking lot.
Paramedics pronounced the baby dead at the scene and her body remained in the parking lot of the mortuary for hours while homicide detectives searched for clues, including surveillance video.
The Los Angeles County Sheriff's Department Homicide Bureau has made contact with individuals believed to be the girl's family members.
An autopsy will be conducted to determine the cause of death for the child, Det. Steve Blagg of LASD Homicide Bureau said.
No further details about the girl's identity or circumstances of her death were immediately available.