Numerous pages of school yearbooks kept in libraries in six prefectures in central Japan were found to have been ripped out, it has emerged.

The latest cases were discovered in five municipal libraries in the cities of Nanao, Kaga and Hakusan in Ishikawa Prefecture. The libraries said Tuesday a total of 173 pages were either torn off or cut out from 14 yearbooks and commemorative publications, including photographs and students' essays. The books are available only for reading and cannot be taken out of the libraries.

The prefecture's board of education also said Monday that three publications from an elementary school, a junior high school and a high school kept in the prefectural library in Kanazawa had been damaged, with pages including class pictures and a list of which schools students got into after graduation removed. The library reported the case to police, they said.

The board of education in the town of Kamiichi, Toyama Prefecture, said it found pages were missing from six school publications kept at the town library.

Similar incidents have been reported this month at libraries in Aichi, Gifu, Mie and Fukui prefectures.

The Japan Library Association, which has 80 percent of public libraries nationwide as members, said it will conduct an investigation into the cases.