The case concerns conditions at its flagship assembly plant in Fremont, California.

It was filed Thursday (September 28) by the U.S. Equal Employment Opportunity Commission.

The civil rights agency says Black workers at Fremont were routinely subjected to racist slurs and graffiti.

That included depictions of swastikas and nooses.

The EEOC says the company has failed to investigate complaints over racist conduct, and fired or retaliated against workers who reported harassment.

The charges are similar to those in cases brought by the state and Tesla employees.

They follow a breakdown in talks between the firm and the agency, which normally settles without going to court.

Tesla did not respond to a request for comment, but has called the previous case brought by the state "politically motivated".

The EEOC suit seeks compensatory and punitive damages for an unspecified number of workers.

One lawyer said the involvement of the federal government lent credibility to claims of harassment, and could alarm investors.