Reuters
This is not the distribution center in question
Amazon Japan is "fully cooperating" with a police investigation, the company told Bloomberg in a statement.
Although Amazon prohibits the sale of any illegal products on its site, and Japan banned the possession of child pornography last year, photobooks and DVDs of pre-pubescent girls are often part of a legal gray area in Japan.
The materials are considered part the "idol industry" - which features young bands and models, often scantily clad.
"It's extremely difficult to say whether these materials can be classified as child pornography," Ryoji Mori, an attorney at Cyber Law Japan Eichi Law Offices in Tokyo, told BusinessWeek late last year. "It's obvious that the target audience is pedophiles, but the manufacturers have done it in such a way that it's difficult to say if it's illegal."
Amazon Japan, Yahoo Japan, and Rakuten all had idol industry content on their sites as recently as October.
"The probe of Amazon Japan may indicate police are now starting to crack down on mainstream retailers that have continued to carry the products," Bloomberg reports.
Disclosure: Jeff Bezos is an investor in Business Insider through his personal investment company Bezos Expeditions.