Electric carmaker Tesla has resumed production at its Fremont, Calif., plant — in defiance of local health authorities.

CEO Elon Musk confirmed the news on Twitter on Monday, after photos of the plant's nearly full parking lot started making headlines. He said he was willing to be arrested if necessary. (Bay Area shelter-in-place orders, which multiple counties have imposed, are largely being enforced by warnings or citations.)

Alameda County says it is expecting Tesla to submit its safety plan for approval, and that until that approval the company cannot resume normal production. The county says it hopes Tesla, like other companies that previously violated the local order, will "comply without further enforcement measures."

Tesla tussled with Alameda Countyback in March, initially defying the county's decision to shut down non-essential businesses. In recent weeks the company's famously erratic CEO has been railing against the shutdown orders on Twitter and in a call with investors.

On Saturday, Musk went so far as to threaten to relocate the plant out of California because of the local shelter-in-place orders, which are designed to limit the spread of the coronavirus pandemic.

Alameda County officials saidthey were "communicating directly and working closely with the Tesla team on the ground in Fremont" in a "collaborative, good faith effort to develop and implement a safety plan" to reopen while protecting workers' health.

Meanwhile, Tesla sued the county, claiming it had no legal right to shut down the plant.

In its lawsuit, Tesla said that an order from California's governor superseded the local health policies, and that under the governor's order Tesla should be allowed to open. On Twitter, Musk again said that Tesla's reopening had been "approved" by the state.

Asked about the plant's reopening on Monday, California Gov. Gavin Newsom said he was unaware that the plant had resumed operations. He said the dispute over the reopening would be resolved "at the county level."

Auto plants across the country are reopening this month. Some plants reopened in early May, while Ford, General Motors and Fiat Chrysler are targeting a May 18 restart.

The timelines for different plants reopening have been shaped, in part, by differing state and local shelter-in-place orders.

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