Tesla has been hit with a complaint from the U.S. agency in charge of enforcing labor law.

The National Labor Relations Board says Tesla has violated the rights of its workers by making them sign a confidentiality agreement stopping them from speaking about working conditions and safety issues at the automaker’s factory in Fremont, California.

Three employees and the UAW filed the complaints and the workers say that Tesla forced them to sign the document alleging they could be terminated or face criminal prosecution for publicly disseminating information about working conditions.

The electric automaker has denied the allegations but must respond to the charges by September 14, Automotive News reports.

The National Labor Relations Board has arranged a hearing before an administrative judge in Oakland, California on November 14.

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