Tokyo metropolitan police have arrested another ex-cram school teacher on suspicion of conspiring to shoot images of a girl's underwear with a former colleague already under arrest.

Police also referred the school to prosecutors for alleged violation of the personal information protection law.

Police identified the newly arrested man as Nakamura Narumi, a 26-year-old former teacher at Yotsuya Otsuka, a major cram school for elementary school children.

Police also served a third arrest warrant for 24-year-old Mori Sosho, who taught at a Yotsuya Otsuka school in Tokyo along with Nakamura.

Mori had earlier been arrested for allegedly taking videos from May to June of an elementary school girl exposing her underwear, along with other acts. Police suspect more than 10 children were victimized.

Police say the girl was a student in his class, and the images were taken in a school building.

Investigators say Nakamura asked Mori in August to take images of another girl in class.

Police say both men admitted to taking the images. Nakamura was quoted as saying he learned Mori was taking sexual images and discussed with him which girl should be the next target.

Police have also referred Mori to prosecutors for alleged violation of the personal information protection law.
Mori is suspected of accessing the school database to get victims' names and addresses and sharing them in an online chat group.

The police also sent papers on Yotsuya Otsuka as a corporation to prosecutors. They say the school's information protection was insufficient.

Yotsuya Otsuka has offered an apology to students, parents and others concerned, and pledged efforts to prevent a recurrence.

The school said such an act should never have happened and it takes the situation seriously. It said it is doing serious soul-searching about its information protection.