More than 30 girls may have been victims in what San Juan County Sheriff Mike Lacy is calling a child pornography case.

Lacy said his office has completed its probe and referred its findings to the Utah Attorney General's Office for possible criminal charges.

As many as eight boys are believed to be involved, though four appear to have been the biggest culprits, Lacy said.

Some of those teenagers have turned 18 and could face charges as adults.

"Some of this has been going on for two or three years," Lacy said. "By the time we got the report, it just kind of snowballed."

In some instances, boys drove girls into the mountains near Monticello. The boys told the girls that if they wanted a ride down, they needed to bare themselves for the camera, authorities said.

Photographs were taken with cell phones and exchanged through cell communication and by computer, Lacy said.

The Utah Internet Crimes Against Children Task Force, based in the Attorney General's Office, participated in the investigation.

John Soltis, the attorney general's office prosecutor assigned to the case, said he is reviewing the evidence but declined further comment.

San Juan School District Superintendent Doug Wright said investigators came to Monticello High School at the start of the school year to interview students. The district told the detectives that administrators must be present in the interviews so the investigators elected to speak to students off campus, Wright said.

Wright said the district has no knowledge of any of the incidents occurring at school, and no students have been disciplined.

ncarlisle@sltrib.com