(Reuters) – The United Auto Workers (UAW) International Union said on Thursday it filed a complaint against electric carmaker Tesla Inc (TSLA.O) on behalf of the company’s terminated workers.

The unfair labor practice charges were filed at the National Labor Relations Board’s (NLRB) Oakland office, the union said.

Tesla in October fired about 400 employees including associates, team leaders and supervisors, Reuters reported, citing a former employee.

Tesla was not immediately available to comment.

UAW said in February it will greet Tesla’s Fremont, California, assembly plant workers with ‘open arms’ in a bid to unionize the factory.

NLRB, the U.S. agency in charge of enforcing labor law, in late August filed a complaint against Tesla, saying it found merit to workers’ complaints about unfair labor practices.