An employee of the Osaka Prefectural Board of Education planted a covert listening device in mid-June at its office in Chuo Ward, the board said Sept. 12.

The bug was found Sept. 11 by a TV crew that was shooting video footage for a program on wiretapping crimes.

On Sept. 12, a male employee in his 40s confessed to his supervisor that he planted the bug, according to the board of education.

The man reportedly told his seniors he had "wanted to check what my colleagues say in their conversations." Then he set up a receiver and eavesdropped on about 20 occasions between mid-June and early August, including during his time at work.