A maintenance worker accused of placing a video camera in the girls' locker room at Oaks Christian School in Westlake Village has been arraigned on 18 misdemeanor charges, including sexual exploitation of minors, authorities said Thursday.

Hilario Hernandez Medina, 39, of Van Nuys, was arraigned Wednesday on eight counts of sexual exploitation of a child and 10 counts of unauthorized invasion of privacy, said Sandi Gibbons, a Los Angeles County District Attorney's Office spokeswoman.

Medina, who appeared in Van Nuys Superior Court, pleaded not guilty to the charges, Gibbons said.

Medina was arrested Monday afternoon at Oaks Christian, said Capt. Joe Gutierrez of the Los Angeles County Sheriff's Department's Special Victims Bureau.

The Sheriff's Department began investigating the case after a school employee found a video camera wrapped in a jacket on a maintenance cart on campus, Gutierrez said.

The employee called police after watching the tape to determine whom it belonged to and discovering that it contained images of girls — apparently in the locker room — in various stages of undress, Gutierrez said.

The number of counts Medina faces stems from a total of 18 girls appearing in the videotape, authorities said. The tape is of poor quality, Gutierrez said.

"We are continuing an investigation with the hope of identifying additional victims," he said.

Medina, a maintenance worker at Oaks Christian who was hired by a contractor about a year ago, was being held in Los Angeles County Jail in lieu of $160,000 bail. He is scheduled to appear in court again June 9.

Officials at the private school, which has grades 6-12, would not identify the contractor who hired Medina but said all contracted employees go through a background check.

Oaks Christian Headmaster Jeffrey Woodcock sent a letter to parents about the matter Tuesday. School officials held a meeting Thursday at nearby Calvary Community Church for parents and students.

"Obviously, we are deeply saddened by the outrageous conduct that was perpetrated and the surreptitious invasion of our campus community," Woodcock said in the letter.

"I ask for your continued prayer for God's grace as we work through this together," he wrote.

Tom Konjoyan, Oaks Christian's director of communications, said counselors were available for students who might want to talk about the matter.

Several parents who attended the Thursday meeting declined to comment. Some students who also attended said they were concerned but felt safe on campus.

"It's a bit scary, but it was something Mr. Woodcock and our school dealt with, because they are concerned with our safety," said junior Danielle Ernest, 17.

"Mr. Woodcock and the staff said they did an electronic sweep of the campus last night, and I feel that it's safe. I think it's a great school, and it's a blessing to be here."

Dan Ernest, Danielle's father, said he did not attend the meeting but was pleased with how the school handled the situation.

"I am glad they caught him now," he said. "They could have prevented an even more serious crime from occurring."