Musk's first email, sent Sunday (June 17), stated an employee had conducted "quite extensive and damaging sabotage to our operation".
CNBC obtained an email sent by Musk to every Tesla worker on Sunday.
Although the company declined to comment on the email officially, several employees confirmed they had received it and shared its full text with the news outlet. Musk said the investigation will continue in an attempt to find out if he was acting alone, or with other people.
Further on in the email, Musk tells Tesla employees that "there are a long list of organizations that want Tesla to die", going on to mention short-sellers, the oil and gas industry, and auto industry competitors. He claims that while these companies cheat about emissions, maybe they can cheat in other ways. "Please be on the alert for anything that's not in the best interests of our company".
Last week, Elon Musk announced that the company would be letting go around 9% of its workforce as part of a "reorg".
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Ending his email, he urges the employees to stay vigilant and report anything suspicious to a particular email address with as much information as possible.
Musk did not specify to whom he was referring. But in a separate email to staff, sent just after 9:30 a.m. on June 18, Musk branded the event "another unusual incident that was hard to explain" and advised all staff to "be on the alert for anything not in the best interests" of the company.
The extent of the disruption isn't clear, but the incident comes at a time when Tesla's production lines have been pushed to the limit trying to meet its target of 5,000 Model 3 sedans per week.
Nancy Tengler, chief investment officer at Heartland Financial, said her firm doesn't own Tesla stock, but she remains "highly amused" by Musk's tweets.
Elon Musk is often compared to Marvel's Tony Stark (sometimes even a spy thriller supervillain) and the latest news out of the company sounds like it was ripped from the script of a summer blockbuster.