TOKYO—Amazon Japan, the Japanese arm of Amazon, the world’s largest online shopping website, is facing an investigation by the Japanese police on suspicion of aiding and abetting the sale of child pornography on its website—a problem that the company should have known about at least since 2009. In that year, as a member of the NGO Lighthouse (formerly known as Polaris Project Japan), we brought attention to the problem in petitions and emails to the company.

The issue is not about Amazon selling this trash itself, it’s about so-called third-party vendors who showcase the porn on Amazon’s site. But according to its critics, the net result is basically the same: Amazon’s accusers say it is facilitating the sexual exploitation of children.

As a member of Lighthouse: Center For Human Trafficking Victims, which combats human trafficking and sexual exploitation, I know we petitioned Amazon by email and in telephone conversations to remove the materials clearly constituting child porn on its website back then. It would seem the company has been, to say the least, slow to do much about it, according to sources close to the investigation.

Now even the Japanese police have launched an investigation.

Japan has been extremely slow to crack down on child pornography, only banning simple possession last year (with a one-year grace period that will soon expire). Selling child pornography is illegal, however, and has been since 1999.

According to the police and the Mainichi newspaper, last summer the Aichi Prefectural Police found photo books on Amazon Japan featuring fully nude pictures of underage girls during an online patrol. They opened a full investigation. In September, police arrested two male owners of a used bookstore for violating the child pornography laws and, later, 10 other vendors in Japan who had broken the law.

Last year, the police searched an Amazon distribution center in Odawara City, Kanagawa Prefecture, and on Jan. 23 of this year, police reportedly searched Amazon Japan’s headquarters in Tokyo as well as a distribution center belonging to Amazon Logistics in Chiba Prefecture, according to police sources and the Japanese media.

Police sources said they suspect that Amazon was aware that vendors dealing in illegal child porn had been selling their products on the website, but chose to ignore the fact despite the company’s guidelines clearly stating that illegal products are not allowed to be sold there. The Aichi Prefectural Police told The Daily Beast that if the suspicions prove to be true, Amazon Japan executives could be charged with aiding in the sale of child pornography.

Officials involved with the investigation, on background, described Amazon’s checks on products sold on the website by third-party sellers as “overly lenient, to say the least.”

According to Sankei Shimbun and other media, many of those purveyors of porn who were arrested made statements along the lines of: “The other big shopping sites would not accept child porn-related products, but I was able to put them on Amazon.”

Lighthouse had been protesting the sale of child pornography since 2007. In 2009 it pointed out in emails and informal talks with Amazon Japan that it had found more than 136 photo books and DVDs featuring swimsuit-clad girls and half-naked boys. While the company gave no formal answer concerning the complaint, over 60 percent of the offensive goods were later removed from the website, according to the NGO.

Shihoko Fujiwara, the founder of Lighthouse, who is also a longtime friend and colleague of mine, recounts the history of what she describes as the sometimes acrimonious back and forth between Amazon Japan and human-rights organizations.

“The products that are considered to be child porn, which Lighthouse had asked Amazon to stop selling five years ago, already are completely illegal in other countries, including the United States, and the overt child pornography is only the tip of the iceberg,” says Fujiwara. “In Japan, as long as the private parts are covered up, there is no crackdown on photographs or video ‘products’ of children who are close to naked. In addition, dozens of shops—starting with Amazon—from big mail-order companies to small shops catering to pedophiles, were able to sell these products. Even now they’re being sold.”

Amazon Japan would not comment to The Daily Beast about what its critics say is its allegedly long history of inaction on the issue but sent the following statement by email:

“We take this investigation seriously and we are cooperating fully with the authorities. We don’t permit illegal items on our site, and we have systems and processes designed to prevent and remove illegal items from being listed. We are committed to enforcing our policies and the law for items listed on our site.

“During the investigation, we are declined[sic] to say any additional comments.”

Angela Kubo contributed to this report.