The child was found by her grandmother around 4 p.m.
"The grandmother went to the store to get some food. She returned home to find the 2-month-old baby in the bath non-responsive," said Anthony Bertagna with the Santa Ana Police Department.
Police were then called to the 500 block of South Sullivan Street. The call was originally for a baby in pool, but upon arrival authorities found the baby not breathing in the Jacuzzi-style tub.
"Out of nowhere we hear the lady screaming, 'Help me, help me!'" said neighbor Jonathan Cruz. "As soon as we went in, I saw her carrying the little baby, and when I saw that I called 911," he said, adding that the baby was naked and wet. He said he tried to perform CPR on the infant, which made her throw up water and blood.
Police are treating the death as suspicious. They say there were indications of child abuse in the death. Family members told police the child's mother was depressed.
"The mother was non-responsive when officers tried to talk to her," said Bertagna.
Police say they did find medication belonging to the mother in the home, but they did not say what the medication was for.
The mother is not currently a suspect, but officials need to interview her. They also need to determine if there was a history of abuse.
"How does a 2-month-old child end up in a Jacuzzi-style tub? That's the main question here," said Bertagna.
After the girl was declared dead by the Orange County Fire Authority, the baby's mother was transported to the hospital for an undisclosed reason. She remained there Friday night.
The mobile home is said to be shared by two separate families.