Authorities were called to a home on Kenmore Drive in Central Fresno's Mayfair District on June 10 for reports of a baby who was not breathing.
Deputies tended to the eight-month-old, but he died at the scene.
An autopsy found the cause of death to be blunt force trauma.
Investigators have interviewed several people at the child's home, and the investigation is continuing. There's no word on any arrests at this point.
Anyone with information is asked to contact the Fresno County Sheriff's Office.