A former Ojai teacher has been charged with 23 counts of sex assault upon a minor, officials announced Friday.

Paul Herder, 65, of Pahoa, Hawaii, pleaded not guilty to the charges, which include lewd act on a child, luring, penetration by a foreign object, oral copulation of a person under 18, unlawful sex and using a minor for sex acts.

The Ventura County District Attorney’s Office also alleges aggravating circumstances that Herder took advantage of a position of trust as a teacher at Oak Grove School to commit the sexual assaults.

Detectives began investigating Herder earlier this year after learning of the allegations against him.

He is believed to have had an unlawful relationship and allegedly engaged in numerous sexual acts with a student between 2013 to 2017 when he worked as a teacher at the school.

Detectives traced Herder to Hawaii in June. He was located and arrested in Pahoa and eventually extradited back to Ventura County on July 31, officials said.

Herder taught at various schools and also provided private tutoring during his career.

Anyone with additional information about Herder is asked to call the Ventura County Sheriff’s Office major crimes unit at 805-384-4722.