according to NBC Chicago.

After conducting an internal investigation, school officials contacted Schaumburg police Monday. On Tuesday, LaDuke was charged with sexual exploitation of a child.

Several students reportedly told police that they were present in the classroom when LaDuke unzipped and lower his pants and then masturbated.

"Through the course of our investigation, our detectives have come to believe that this has happened several times per year for 10 years or more, possibly," Schaumburg police Sgt. John Nebel told the CBS affiliate in Chicago.

"It’s not that it’s been reported and nothing has been done, it’s just that during the course of the investigation, we’ve come to learn certain information and I can’t go further for the fact that there’s a possibility of more charges before a grand jury," he added.

Police say that there is no evidence that LaDuke, who taught Algebra, Geometry and Trigonometry/Pre-Calculus, had inappropriately touched any students.