A US civil rights agency sued Elon Musk’s Tesla on Thursday, claiming the electric carmaker has tolerated severe harassment of black employees at its flagship Fremont, Calif., assembly plant.

The Equal Employment Opportunity Commission said in the lawsuit filed in California federal court that from 2015 to the present, black workers at the Tesla plant have routinely been subjected to racist slurs and graffiti, including swastikas and nooses.

Tesla has failed to investigate complaints of racist conduct and has fired or otherwise retaliated against workers who report harassment, the EEOC said in the lawsuit.

Tesla is already facing several race discrimination lawsuits that make similar claims, including a class action by workers at the Fremont plant and a lawsuit by a California civil rights agency.

The company has denied wrongdoing in those cases.