The closure, which is expected to come at the end of the month according to Tesla blog Electrek, is necessary to install new heavy machinery to speed up production — likely of the company’s new Model Y SUV — and could take several days or a week.

“Some workers were told that factory shutdown is expected by the end of the month,” according to the blog.

Tesla’s Fremont factory is its most important facility, and Musk has made upgrades at the plant a priority. The factory is so crucial to Tesla’s business that Musk railed against California health officials when they forced it to shut down during the state’s coronavirus lockdown.

It is also the site of a recent surge in cases of the virus, with hundreds of workers having been infected or having come in contact with someone who was infected in recent months.

While Tesla has implemented measures meant to keep employees safe, such as temperature checks and mandatory social distancing, employees told Electrek that rules are not always followed.

The Washington Post reported in June that half a dozen anonymous Tesla workers said that the Northern California factory was lax in enforcing its safety measures, including the sanitation of machinery.

The report alleged that factory employees are “hovering over each other,” and that there is a lack of communication between management and staff regarding coronavirus cases among workers. Employees disappear for weeks at a time, according to the report, with supervisors saying only that they were “sick.”

Shares of Tesla were down 1.2 percent Wednesday morning, at $1,499.02. The company, which recently eclipsed Toyota to become the most valuable automaker in the world, now has a market cap of $277.9 billion.