Tesla's main factory in California has begun a three-week lockdown to slow the spread of coronavirus.
It will be a blow to plans to ramp up production of the Model Y electric vehicle, for which the company had been expecting high demand.
Chief executive Elon Musk had said he hoped to continue manufacturing and delivering cars as normal.
Alameda County, where the factory is based, is limiting travel and business functions to only the most essential.
Mr Musk had previously written to workers, saying work at the Fremont plant would continue but they should not feel obligated to come in.
"My frank opinion remains that the harm from the coronavirus panic far exceeds that of the virus itself," he wrote in an email to employees.
He has also tweeted similar thoughts.
The San Francisco Bay Area counties have reported 273 coronavirus infections and California has reported 12 deaths from Covid-19.
The factory employs more than 10,000 workers and records annual production of about 415,000 electric vehicles.
Tesla had to shut down its Shanghai plant for 10 weeks, when the virus was at its peak in China.
Under the new order in Alameda County, businesses deemed non-essential can continue only minimum basic operations, such as maintaining the value of inventory, ensuring security and processing payroll and employee benefits.