Missing Autistic Girl - CA *UPDATE*:Missing girl found dead (update in first comment)
**See the first comment for the update information:
Authorities continue to search for a 9-year-old autistic girl who disappeared from her family's Clearlake, Calif., vacation home on Mother's Day.
Mikaela Lynch, of San Francisco, was reported missing from her fenced-in backyard where she had been playing with her younger brother, ABC's San Francisco affiliate KGO-TV reported. Lynch's brother reportedly ran inside to avoid a bee, and left the gate open and his sister unattended.
Bari Lynch, Mikaela's mother, contacted police to report her daughter missing just before 1:30 p.m. Sunday, according to the Clearlake Police Department.
Police said in a statement that the missing girl cannot speak, and given her "mental state, age and circumstances, ... is believed to be an at risk missing juvenile."
A woman who answered the phone at the Clearlake Police Department told ABC News that authorities did not believe Mikaela had been abducted, and that rescue workers were concentrating their search efforts on land and in the water around Lake County.
"She does like water. The residence does back up to waterways," Clearlake Police Lt. Tim Celli told the Santa Rosa Democrat. "As far as we know, she does not swim."
It is believed that Mikaela is naked and shoeless, as police found her clothing in the family's yard.
KGO-TV reported that some of the teachers at Sunset Elementary School in San Francisco, where Mikaela is enrolled, took Monday off to help search for the missing girl.
Haben Porter, a teacher at the school, described Mikaela as "very inquisitive."
"She likes to explore and climb," Porter told KGO-TV. "It's just kind of part of who she is."
Nearly half of all children with autism will run away and potentially go missing at least once before their 17th birthdays, according to a study by the American Academy of Pediatrics. Of those who run away, what clinicians call "eloping," many will be found dead.
In 2012, 195 autistic children went missing, according to the National Autism Association, which only tracks the disappearances reported by the media.
Between 2009 and 2011, 91 percent of autistic children younger than 14 died in drowning incidents after "elopements." More than two-thirds of those deaths occurred in small natural bodies of water, such as creeks, lakes, rivers and ponds, acccording to the National Autism Association.
Still, Clearlake Police Chief Craig Claussen told KGO-TV he was "hopeful about the search."
ABC News' Russell Goldman contributed to this report.