ST. PAUL, Minn. (AP) — Federal prosecutors have charged a former Bemidji assistant principal with child pornography and trying to entice a minor.

The U.S. Attorney's office says 34-year-old Brandon Mark Bjerknes of Bemidji appeared in federal court Wednesday.

Bjerknes served as assistant principal of Bemidji Middle School for the past three years until he resigned in April. The complaint alleges Bjerknes posed as a teenage boy and used social media profiles on Facebook and Snapchat with "decoy photographs" to contact girls and boys in middle and high school. Using the alias profiles, Bjerknes allegedly directed the victims to send him sexually explicit photographs and also engaged in sexually explicit conversations.

Authorities say Bjerknes contacted more than 50 victims, and there may be more victims.