A group of Republican congressmen are calling on federal regulators to blacklist two Chinese battery manufacturers they say are using forced labor to make their products.

The lawmakers sent two letters to the Department of Homeland Security, saying that Chinese companies Gotion and CATL are using state-sponsored slave labor by minority populations and that they’ve expanded their U.S. presence.

Reps. John Moolenaar, R-Mich., Mark Green, R-Tenn., Carlos Gimenez, R-Fla, and Darin LaHood, R-Ill., and Sen. Marco Rubio, R-Fla., urged the department to add the companies to the “entity list” that bans from the U.S. products made by companies believed to be using forced labor.

The Biden administration has been separately taking steps to limit electric-vehicle batteries and battery materials from the U.S. market, in part by tying EV tax credits to vehicles with limited materials from Chinese and other “foreign entities of concern.” Last month, it did temporarily ease the restrictions to give U.S. automakers more time to comply.

China holds much of the world’s supply of some EV battery materials, such as graphite, but the U.S. is trying to speed development of domestic sources and battery manufacturing to eliminate dependence on its transpacific rival.

Moolenaar, chairman of the House Select Committee on the Chinese Communist Party, said in a statement on the letters, “The American people expect companies in the U.S. to avoid all involvement with the Chinese Communist Party’s campaign of genocide.”