Rocket and satellite maker SpaceX on Wednesday was accused by a U.S. labor agency of unlawfully firing eight employees for circulating a letter calling founder and CEO Elon Musk a "distraction and embarrassment."

A regional official with the National Labor Relations Board (NLRB) issued a complaint claiming SpaceX violated the workers' rights under federal labor law to band together and advocate for better working conditions.

The letter sent to SpaceX executives in June 2022 focused on a series of tweets Musk had made since 2020, many of which were sexually suggestive. The employees claimed Musk's statements did not align with the company's policies on diversity and workplace misconduct, and called on SpaceX to condemn them.

The complaint also accuses SpaceX of interrogating employees about the letter, disparaging the workers who were involved, and threatening to fire workers who engaged in similar activity.

SpaceX did not immediately respond to a request for comment.

SpaceX has a "toxic culture" where harassment is tolerated, particularly against women, Deborah Lawrence, one of the employees who was fired, said in a statement provided by her lawyers.

"We wrote the open letter to leadership not out of malice, but because we cared about the mission and the people around us," Lawrence said.

The NLRB's general counsel acts like a prosecutor and brings cases to the five-member board appointed by the president.

If SpaceX does not settle, the case will be heard by an administrative judge, whose decision can be appealed to the board and then to a federal appeals court. A hearing is scheduled for March 5.

When the NLRB finds that firings violated labor law, it can order that workers be reinstated and given back pay. If SpaceX is found to have violated the law, it could also face steeper penalties in future cases before the board.

The case is the latest to accuse companies run by Musk of violating employees' rights under labor and employment laws.

Reuters in November documented at least 600 previously unreported workplace injuries at SpaceX facilities, including crushed limbs, electrocution, head injuries and one death. SpaceX did not respond to requests for comment on the findings.

In October, the NLRB issued a complaint accusing X, the Musk-owned social media service formerly known as Twitter, of illegally firing an employee over tweets challenging the company's return-to-office policy. X has denied wrongdoing.

And electric vehicle maker Tesla Inc, where Musk is CEO, has faced several NLRB complaints amid a union organizing campaign and numerous lawsuits alleging widespread race discrimination at its factories. Tesla has said it does not tolerate discrimination.