Deputies responding about 8:10 a.m. to a baby-not-breathing call in the 11100 block of South Normandie Avenue found a woman "outside the location performing CPR on an infant,'' said Deputy Trina Schrader of the Sheriff's Information Bureau.
The woman directed the deputies to another person inside who needed help, Schrader said, and they "found a female adult inside the location that was unresponsive.''
The infant and the woman were pronounced dead at the scene by county fire department personnel, Schrader said.
Ed Winter of the Los Angeles County coroner's office said the woman was in her 20s, but the names and causes of death of the woman and child were not immediately released.
Sheriff's homicide detectives were looking for Algernon Rieux, 26, who they say is bipolar and may be on suicidal and under the influence of methamphetamine.
Rieux is the woman's husband and the child's father, according to reports from the scene.
Rieux is described as black, 5 feet 7 inches tall and weighing 160 pounds. He has connections to the San Pedro area.
Anyone with information regarding his whereabouts was urged to call the Sheriff's Homicide Bureau at (323) 890-5500. Anonymous tips can be provided by calling Crime Stoppers at (800) 222-TIPS.