The investigation began when a woman in her early 20s, who appeared to have recently given birth, arrived at a Woodland Hills hospital just before 6 p.m., according to the Los Angeles Police Department.
Police said the woman showed up at an emergency room, and officers then went to her residence in the area of Burbank Boulevard and Woodlake Avenue.
Upon arrival, police found the newborn deceased. The infant is believed to be a day old.
Police said they are investigating the death as a homicide. Authorities have not said if the mother will be arrested or face any charges.
1-day-old infant found dead in Woodland Hills
Neighbors in the area told Eyewitness News off-camera that they didn't really know the people who lived in that home.
Some wondered why the newborn wasn't safely surrendered.
Under California's Safely Surrendered Baby law, parents or legal guardians can legally and safely surrender their infant at any hospital or designated fire station within 72 hours of birth, no questions asked.
Information about the program and locations in Los Angeles County is available here or by calling 1-877-222-9723.
Since the program was launched in L.A. County, more than 250 infants have been safely surrendered, according to the website.