Pasadena police say the 2-year-old's mother made a frantic 911 call around 6 a.m. Tuesday, saying her child was not breathing.
When authorities arrived at the home in the 500 block of Summit Avenue they found the little boy in his crib unresponsive. Paramedics tried to revive him, but the toddler was pronounced dead at the scene.
Homicide detectives have been talking with family members to try to determine what may have happened to the toddler.
"You have a healthy 2-year-old that dies, it feels suspicious," said Janet Pope-Givens from the Pasadena Police Department. "We don't know what that is and until we can determine any other causes at this point we're going to launch a police investigation."
Detectives are awaiting the autopsy to determine exactly how the boy died.