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A Barstow High School teacher is out on bail after being arrested amid a probe into an inappropriate relationship she was alleged to be having with an underage student, officials said Monday.

Authorities began investigating 51-year-old Katherine O’Neill, of Barstow, after someone came into the local sheriff’s station last Thursday to report the teacher was sexually abusing a 16-year-old girl, San Bernardino County sheriff’s officials said in a news release.

O’Neill has already been on administrative leave since October, deputies said. Before that, she had taught American government and history classes at the high school on First Avenue, according to the school’s website.

Detectives interviewed the student victim about the allegations and determined the teen and teacher had indeed been engaged in a sexual relationship. In addition to physical abuse, O’Neill is accused of sending the girl explicit text messages with obscene material, authorities said.

Investigators say the crimes occurred at various locations within Barstow.

It was unclear whether the student was in any of O’Neill’s classes.

The teacher was arrested Friday on suspicion of penetration with a foreign object, oral copulation with a minor, annoying and molesting and sending harmful matter to a minor.

O’Neill was released from custody the next day after posting $100,000 bail, officials said.

A court appearance has yet to be scheduled, inmate records show.

Detectives believe O’Neill could have additional victims.

Anyone with information can contact Deputy Gerania Navarro at 909-387-3615 or Detective Brian Grimm at 760-256-4838. Anonymous tips may be submitted via 800-782-7463.

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