Tesla is facing new allegations of labor violations. Union organizers filed four complaints with the National Labor Relations Board alleging misconduct toward employees interested in unionizing at the Fremont plant, the Silicon Valley Business Journal reports.

The complaints, originally reported by BuzzFeed, accuse the electric car manufacturer of intimidating three employees who were offering pro-union information to other employees in February. The employees were allegedly told they could not pass out information unless it was approved by the company.

Since 2011, there have been seven investigations into Tesla’s labor practices from employees at Fremont, Palo Alto and Austin, but each of those investigations were closed. United Automobile Workers is attempting to unionize workers at the Fremont plant. Tesla CEO Elon Musk has argued against unionizing.

Tesla previously was warned by state lawmakers that its employee confidentiality agreement is too broad and keeps workers from engaging in protected activities, according to BuzzFeed.

Workers are barred from sharing information about products, communicating with the press, posting or sharing videos of the factory and writing about the workday on any form of media. Tesla has said its confidentiality agreement is standard among tech companies.

The automaker is undergoing a massive expansion and plans to build 500,000 vehicles by next year. It also is expanding its electrical charging station capabilities to keep up with demand.