Last week, the Palo Alto-based automaker said it was cutting about 9% of its workforce - about 3,600 mostly white-collar employees - in an attempt to become profitable.
Musk said in the email that while the fire could have been a random event, "Please be on the alert for anything that's not in the best interests of our company".
In various statements in public and recently to Tesla employees, Musk has said that he routinely lives around the clock at the manufacturing plant while the company tries to increase production of the Tesla Model 3, a mass-market sedan that now starts at $44,000.
"The full extent of his actions are not yet clear, but what he has admitted to so far is pretty bad", Musk wrote in the email, according to Electrek and CNBC. "His stated motivation is that he wanted a promotion that he did not receive".More news: PlayStation Hits re-releases top PS4 games on the cheap
Tesla is conducting an in-depth investigation into the matter, including whether the employee was acting alone, with others at the company or with any outside organizations, Musk wrote.
The organizations that Musk believes could be responsible include the petrochemical industry, the traditional automotive manufacturers and Wall Street short-sellers, but given the relatively huge number of people that the company is laying off as part of its path to profitability, that seems to be a more likely culprit.
The email was sent the same night a fire shut down operations at a Tesla plant in Fremont, California, for several hours. And while we're still a ways away from a Tesla driving itself from LA to NY with zero driver interaction - something Elon Musk promised would go down in 2017 - there's no denying that Tesla's Autopilot feature, when used as intended, can truly help reduce the incidence of accidents and deaths on the road.
Most of the time, when there is theft of goods, leaking of confidential information, dereliction of duty or outright sabotage, the reason really is something simple like wanting to get back at someone within the company or at the company as a whole.
Tesla shares climbed for a seventh straight day, adding 3.5 per cent to $370.83 on Monday. (TSLA) gears up to produce 5,000 Model 3 cars a week by the end of June, its founder and CEO, Elon Musk, is on a mission to prove the skeptics wrong.