5Dimes, a gambling site based in Costa Rica, allegedly told its U.S.-based customers to purchase Amazon gift cards at retail stores in cash to fund their accounts, according to Re/Code. The Department of Homeland Security has applied for a grant of seizure with the Philadelphia U.S. District Court to access more than $150,000 stored in Amazon accounts associated with the site.

But that’s just a small slice of the total amount of cash that’s flowed through Amazon accounts linked to 5Dimes. The Department of Homeland Security estimated that as much as $1.9 million passed through these accounts over the years.

“[T]he investigation has determined that 5Dimes has developed an alternative to the traditional online financial payment methods, which is unavailable to 5Dimes under federal law, in order to operate its illegal betting operation in the U.S.,” the filing said, according to Re/Code. Using Amazon gift cards for this purpose is against the company’s terms of service.

A 5Dimes spokesperson declined to comment for this article.

Fortune has reached out to Amazon for comment and will update this post if the company responds.