A 28-year-old Fairfax County teacher has been charged with possession of child pornography, authorities said Thursday.

       Kristine Knizner, of Springfield, is facing two felonies following an investigation that began with a tip from the National Center for Missing and Exploited Children (NCMEC). At the time of her arrest, Knizner was a teacher at Irving Middle School in Springfield and before that was a teacher at Key Middle School in Franconia.

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       Police said they have not found any offenses involving Fairfax County students.

       The investigation began when the NCMEC reported to Fairfax County police that a person with a Snapchat account with an IP address in Fairfax County was in possession of child sex abuse material, police said.

       The IP address returned to Knizner’s Springfield apartment. She was arrested and charged with two counts of possession of child pornography. Knizner was taken to the Fairfax County jail, before being released on a $2,000 bond.

       Knizner did not immediately respond to a request for comment and no attorney is listed for her in court records. Fairfax County schools wrote in a letter to parents that Knizner has been placed on leave.