Tesla Chief Executive Elon Musk has said that the company can make no new hires unless he personally approves them, including contractors, the Information reported on Monday, citing an email to staff.

According to the report, Musk told executives to send him a list of hiring requests on a weekly basis, while also cautioning them to “think carefully” before submitting such requests.

Tesla did not immediately respond to a Reuters request for comment.

Musk named former NBCUniversal advertising chief Linda Yaccarino as Twitter’s new CEO last week. He said on Friday that hiring Yaccarino would allow him to spend more time to run Tesla.

The billionaire is expected to address Tesla shareholders on Tuesday at the automaker’s annual meeting at its headquarters in Austin, Texas.