The agency, called the Federal Cartel Office, said on Thursday that it’s investigating Amazon’s Marketplace to determine whether it’s hurting third-party sellers trying to sell products through its website. The agency told the Associated Press that it received “many complaints” and will investigate “whether Amazon is abusing its market position to the detriment of sellers active on its Marketplace.”

Amazon’s Marketplace allows third-party sellers to sell their products alongside those that Amazon itself sells through its online store. In some listings, shoppers will see products listed and have the option of clicking a link to see prices at other sellers through the Amazon Marketplace. In some cases, pricing can be better and in others, worse. Products sold through the Marketplace can be new, used, or refurbished.

Amazon has touted its Marketplace as an opportunity for small retailers to access its hundreds of millions of customers. Amazon also says that its Marketplace helped third-party sellers sell more than 2.1 billion euro ($2.4 billion) in product in 2017.

In a statement to Fortune, an Amazon spokesperson said that the comment does not “comment on ongoing proceedings.” The spokesperson added, however, that it will “cooperate fully” with the German antitrust agency and Amazon will “continue working hard to support small and medium-sized businesses and help them grow.”