The Oakland regional office of the National Labor Relations Board filed a complaint against electric car giant Tesla Inc. TSLA on Thursday, claiming the automaker interfered with its employees' union activities at Tesla's Fremont, California manufacturing factory.

The NLRB complaint reaches back to claims made in April, when the United Automobile Workers union filed four separate charges with the board claiming that Tesla had "illegally surveilled and coerced factory workers attempting to distribute information about the union drive," according to Buzzfeed News.

The complaint filed yesterday by the NLRB provides more details on what happened earlier this year, noting things like security guards asking employees distributing pamphlets to show employee ID cards, then proceeding to tell them to leave factory premises, to naming three individual Tesla managers who questioned employees about union activities or tries to prevent employees from talking about union activities.

NLRB's complaint also cites Tesla's restrictive confidentiality agreement, a document that prohibited employees from organizing or discussing their work condition, notes Inc. While Tesla argues that this document is typical of any tech company, California lawmakers warned the company back in February that the agreement was overreaching.

Based on these findings, NLRB regional director Valerie Hardy-Mahoney wrote that the automaker "has been interfering with, restraining and coercing employees in the exercise of their rights."

Tesla has stood firm in its dismissal of the UAW's allegations, saying "For seven years, the UAW has used every tool in its playbook: misleading and outright false communications, unsolicited and unwelcomed visits to the homes of our employees, attempts to discredit Tesla publicly in the media, and now another tactic that has been used in every union campaign since the beginning of time…".

"These allegations, which have been filed by the same contingent of union organizers who have been so outspoken with media, are entirely without merit. We will obviously be responding as part of the NLRB process," Tesla continued.

The NLRB's complaint is likely the last thing Tesla wants, especially as production on its highly-anticipated Model 3 begins to ramp up. CEO Elon Musk already warned investors, however, that the electric car maker may face some manufacturing challenges in the coming months.

The board's complaint is set to be reviewed by an administrative law judge at a hearing next week.

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The views and opinions expressed herein are the views and opinions of the author and do not necessarily reflect those of Nasdaq, Inc.