Electric car firm Tesla has been ordered to keep its main plant in the US closed, as California grapples with a coronavirus outbreak.
Chief executive Elon Musk had told staff "limited" production would resume on Friday at the Fremont factory, near San Francisco, according to CNBC.
But Alameda County says this could lead to a spike in coronavirus cases.
Nearly 9,500 cases have been reported in the San Francisco Bay Area, along with 342 virus-related deaths.
Since 23 March, all but "basic operations" have been suspended at the plant because of "shelter in place" orders enacted in the county. The factory employs more than 10,000 workers, and makes about 415,000 vehicles every year.
California's government has eased some restrictions around the state this week, allowing businesses to resume operations. But several Bay Area counties, including Alameda, have issued their own criteria according to which businesses may reopen, which take precedence.
"Tesla has been informed that they do not meet those criteria and must not reopen," Alameda County said in a statement. "We welcome Tesla's proactive work on a reopening plan, so that once they fit the criteria to reopen, they can do so in a way that protects their employees and the community at large."
Tesla did not immediately respond to the BBC's request for comment.
Mr Musk has drawn controversy for his opposition to coronavirus restrictions, and his promotion of unproven treatments for the virus.
In a series of tweets, the tech billionaire has said "the coronavirus panic is dumb" and "FREE AMERICA NOW".
It comes as Tesla has suspended operations at its plant in the Chinese city of Shanghai, according to Bloomberg. It had previously closed the factory as a temporary measure when the virus was at its peak in China.
The company reported a net profit in the first three months of this year, and its stock has risen to nearly $820 (£669; €756). But analysts expect the coronavirus pandemic will adversely affect its earnings in 2020.