UPDATE: Mikayla Anderson was found safe Friday afternoon.
Search and rescue teams combed a rural area of Huasna Valley for the missing 12-year-old girl for nearly 24 hours.
San Luis Obispo County sheriff's officials said Mikayla Anderson was last seen leaving Paulding Middle School Thursday afternoon.
One hundred people from San Luis Obispo, Santa Barbara, Ventura and Kern counties searched the rugged terrain through areas known to be frequented by bears and mountain lions in the past, according to officials.
Six K-9 units helped with the search, as well as two helicopters and one plane.
Anderson's family told NewsChannel 3 she was going on horseback riding near her grandmother's home in the Huasna area Thursday after school.
Around 5 p.m. on Thursday, deputies found her horse but no sign of Anderson.
"She went on horseback and went on a ride. She ended up tying up her horse in this vicinity and set off on foot," said Tony Cipolla, San Luis Obispo County Sheriff's Department.
Just after 4 p.m. on Friday, the 12-year-old was found and taken to the hospital as a precaution.