Authorities in Japan have raided Amazon.com Inc.’s offices in Tokyo as part of an ongoing antitrust investigation, local media reports said Sunday.

The raid was said to have been carried out by Japan’s Fair Trade Commission late last week, in a bid to collect evidence for its probe into the company. An Amazon spokesperson told SiliconANGLE it was “fully cooperating” with Japanese authorities.

The JFTC’s investigation is said to revolve around complaints over how Amazon has treated some of its vendor partners in the country. The Guardian cited local news outfit Asahi Shimbun as reporting that some suppliers complained of being told to pay a “collaboration fee,” which is measured as a percentage of the selling price of certain products. The fees were reported to be designed to cover discounts offered on the Amazon Japan website.

Amazon reportedly told suppliers that it would stop working with them if they declined to pay the fees. The JFTC declined to comment on the reports.

This isn’t the first time that Amazon has faced regulatory scrutiny in Japan. Back in 2016, the company saw its offices raided by the same agency as part of another antitrust probe. The JTFC later found that Amazon had unfairly told its suppliers to sell products on Amazon Japan at the same price or a lower price than listings on other platforms.

Japanese law prohibits companies from abusing their superior bargaining position by forcing business partners to accept trade conditions that could be unprofitable. Following that earlier investigation, Amazon agreed to drop the practice, the Guardian reported.

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