SAN DIMAS, Calif. — Authorities say the diary of a Southern California teacher's aide reveals her sexual relationship with an underage student and that she gave birth to the boy's baby.

Sgt. Peter Hahn of the Los Angeles County sheriff's special victim's bureau says 31-year-old Mandy Morales was arrested at her home Wednesday after prosecutors filed charges Tuesday that she had unlawful sex with a minor.

She's free after posting $50,000 bail. Authorities didn't immediately know if she had an attorney.

Hahn says the victim was 16 when the sexual relationship began in 2011.

Officials at Canyon View School in San Dimas said Thursday that they no longer employ Morales and they're cooperating fully with investigators.

On its website, the school says it offers specialized programs and individual attention to students.