A man accused of holding a 13-year-old girl as a sex slave in a remote motor home in Moorpark was arraigned on rape charges Wednesday.

Shawn Barth, 46, held the girl prisoner since May and sexually assaulted her daily, Detective Eric Buschow said. He said she was too afraid to report the abuse because Barth threatened her.

"She was a psychological prisoner," Buschow said.

Barth was charged in Ventura County Superior Court with a felony count each of child rape, continuous sexual abuse and oral copulation on a child.

The girl was taken into protective custody last week and her name has not been released.

She was the daughter of a woman Barth had dated in San Bernardino County, Buschow said. The mother is a witness in the case and is cooperating with police.

He could not provide further information on why the girl was living with Barth, who claimed to be her legal guardian. She was not reported missing.

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Barth allowed the girl to attend school, but he kept her isolated in the motor home he parked in an orchard at least a mile from the nearest road, Buschow said.

Authorities began investigating Barth after the Moorpark school district asked for a routine transfer of the girl's records from her old school in San Bernardino County.

Yucaipa school officials said there had been previous molestation allegations against Barth. Moorpark school officials became suspicious and reported the girl to police.

Buschow said investigators believe Barth and the girl may have traveled around Southern California in the motor home before settling in Moorpark.

Sheriff's deputies trailed Barth for five days before arresting him Monday.

Officials said there could be other victims.

Barth was being held on $1 million bail. His next court date is Oct. 2.