Police said Tuesday that a man in his 30s has been arrested on suspicion of secretly filming female students at a private academy, as well as other women in public spaces, to produce exploitative content.

Gangwon Provincial Police said the suspect is accused of using smartphones to secretly film 17 female students under their uniform skirts 141 times from January 2020 to October, while he was working at a private cram school, or hagwon, in Gangwon Province. The man then created 1,810 pieces of sexually exploitative content with the footage.

He is also accused of filming the body parts of 261 adult women at cafes, convenience stores and fitness centers and producing and possessing 2,843 pieces of explicit material.

It was reported that the size of sexually explicit material created from student victims reached 9,000 gigabytes, while the footage produced for adult victims reached 1.71 terabytes.

The crime was uncovered after the police received an anonymous tip from a worker who noticed a man acting suspiciously with his cell phone and appearing around the same time in areas frequented by teens.

The police tracked the suspect’s movement and uncovered details of his activities. Through three months of investigation -- including using CCTV footage, telecommunications and financial records -- the police identified the suspect and were able to apprehend him.

The investigation revealed the man used an altered smartphone, which did not make a shutter sound during filming, as well as a smartwatch, to commit the crimes. Police said there was no evidence of distributing the produced materials online. To prevent any secondary damage, police are working with the Korea Communications Standards Commission and the Ministry of Gender Equality and Family to monitor online and delete content should any emerge.

The police are continuing their investigation into the man with the possibility of discovering additional crimes.