The Board of Education in Ikoma City, Nara Prefecture, says that several 8th grade junior high school boys are suspected of voyeuristically filming up the skirts of their female classmates.

According to the board, the municipal junior high school, which has not been named, stated it had launched an investigation into the alleged criminal offense, Sankei Shimbun reported. The board said the voyeuristic filming started last November and involves at least six or seven male students.

The boys used their smartphones or a pen equipped with a small camera to covertly film up the skirts of at least 20 female classmates without their knowledge on several occasions at school. The students shared the images on the free messaging app Line in exchange for between 300 and 1,000 yen.

The incidents came to light on Feb 7 after several students who were not involved in the filming reported it to the school. That same day, the board of education was contacted by the school and notified police.