The girl was unconscious and rushed to the hospital where she was pronounced dead.
It is unclear why 911 was called or who called.
Gallagher said emergency room doctors indicated she may have been sexually assaulted.
The coroner's office's preliminary findings were inconclusive, officials said.
Detectives are waiting for the results of an autopsy, but called her death suspicious.
Officials did not say who was in the house with the girl at the time.
"I see them just about every day," said Edward Williams, who owns a nearby store. "I'm just surprised and kind of shocked."
Anyone with any information about the girl is asked to call the sheriff's special victims bureau at (866) 247-5877.
The Associated Press contributed to this report.