Police have raided offices of the Japanese arm of U.S. online retailer Amazon.com Inc. on suspicion of assisting the sale of child pornography, investigative sources said Saturday.

The Tokyo headquarters of Amazon Japan K.K., its affiliate and a distribution center in Chiba Prefecture were searched Friday for evidence they broke the law against public display of child pornography.

Amazon Japan is suspected of helping sales of child pornography such as photo books of nude girls under 18 by leaving them on its website despite knowing they had been posted there, the sources said.

“We can’t comment on individual cases. If we receive any request from investigative authorities, we would respond based on laws,” said an Amazon representative.

The Aichi Prefectural Police recently found books containing images of underage girls on sale on Amazon Japan’s website and arrested two men last September in connection with the case.

Another Amazon distribution center in Odawara, Kanagawa Prefecture, was raided in November.

Amazon Japan’s guidelines ban the sale of illegal products, stolen items and sex-related goods, including child pornography.