The Uyghur Forced Labor Prevention Act went into effect in June to prevent U.S. imports of products that come from Xinjiang, where Chinese authorities reportedly put up forced labor camps to house Uyghur Muslims and minority groups.

The act provides The U.S. Customs and Border Protection (CBP) with discretion over which companies’ imports should be banned, and its list currently includes several makers of solar-grade polysilicon, a raw material used to produce solar panels.

The Democratic representatives asked why JinkoSolar Holding Co Ltd, Xinte Energy Co Ltd and Longi Solar were left off the list since all three were included in a 2021 report from Sheffield Hallam University that found signs of ties to forced labor in solar supply chains.

“The United States cannot stand by as the Chinese Communist Party tries to flood our markets with goods made by forced labor and harm American workers in the process,” said Ryan on Twitter.