The prices of frozen potato products—dominated by four companies—increased 47% in just two years, alleges one lawsuit.

Four companies currently dominating a multibillion-dollar market in the United States are being accused of sharing detailed, sensitive inside information with each other as part of an alleged conspiracy to raise the price of their goods and make more money off consumers.

Redner’s Markets Inc. has filed a federal lawsuit claiming collusion by a “potato cartel” has caused prices of frozen potato products to soar by 47%.

Four major players in the American potato market are facing allegations of collusion to artificially inflate prices of frozen potato products. The companies involved in this case — McCain Foods, Cavendish Farms,