On Wednesday, July 3, Medics responded to the building on the 2300 block of Mission Street and rescuers had to break down part of a fence to reach the child.
The baby boy was transported to the hospital, but later died.
The Office of the Chief Medical Examiner identified the baby and notified family members, but gave no other information.
Child Protective Services had been notified of the incident last week and were conducting their own investigation.
The fire department is also investigating and anyone with information is asked to call the SFPD Tip Line at 1-415-575-4444 or Text a Tip to TIP411 and begin the text message SFPD. You may remain anonymous.