(Bloomberg)—Amazon.com Inc.’s office in Japan was searched by Japan’s Fair Trade Commission over its dealings with merchants who sell goods on its online web store, a person with knowledge of the matter said.

The antitrust agency is looking into whether Amazon, No. 4 in the Internet Retailer 2016 Asia 500, sought deals with sellers that gave it more favorable conditions over other e-commerce companies, said the person, who asked not to be identified because the information isn’t public.

A spokeswoman for Amazon, declined to comment. A representative for the JFTC also declined to comment. The Nikkei newspaper first reported the inquiry into Amazon’s business practices.

Japan is one of Amazon’s biggest international markets. Overseas sales made up 32% of the Seattle-based web retailer’s revenue in the latest quarter. Amazon debuted in Japan in 2000 as the company’s first website in Asia, and now offers Prime membership, which includes video, same-day shipping and other add-on services for an annual fee.

It wasn’t immediately clear when the JFTC inquiry took place. Under Japan’s antitrust laws, businesses aren’t allowed to impose restrictions on the commercial activities of counterparties.