"Tesla is restarting production today against Alameda County rules," Musk tweeted on Monday. "I will be on the line with everyone else. If anyone is arrested, I ask that it only be me."
On Tuesday morning, the auto industry tycoon followed up in a tweet saying that it went "Great" at the factory on Monday.
The Tesla plant in Fremont, California, employs more than 10,000 people. In a statement on their website announcing reopening plans, Tesla argued it has "a responsibility to look out for the livelihoods and safety of our personnel, many of whom rely on us and have been out of work for weeks due to the impacts of shelter-in-place orders."
The automaker also outlined a series of safety measures it was enforcing as it reopened, including mandatory social distancing and enhanced cleaning measures.
Alameda County officials said Monday that they were aware of the factory reopening and that they notified Tesla that "they can only maintain Minimum Basic Operations until we have an approved plan that can be implemented in accordance with the local public health Order."
"We are addressing this matter using the same phased approach we use for other businesses which have violated the Order in the past, and we hope that Tesla will likewise comply without further enforcement measures," Neetu Balram, the public information manager for the county's public health department, added in a statement.
Balram added Monday that they look forward to reviewing Tesla's site-specific plan for reopening beyond Minimum Basic Operations.
President Donald Trump, who has been an outspoken supporter of reopening the economy, weighed in the saga on Twitter Tuesday morning, siding with Musk.
"California should let Tesla & @elonmusk open the plant, NOW," the president tweeted, adding that it can be done "Fast" and "Safely!"
Medical authorities have urged against mass reopening plans in the absence of a vaccine, widespread antibody testing or an effective treatment for COVID-19.
On Saturday, Tesla filed a lawsuit against Alameda County, arguing in court documents obtained by ABC News that the plant is part of California's governor-outlined "critical infrastructure" and has the right to reopen despite local officials ordering the opposite.
Alameda County's Public Health Department responded in a statement Saturday, saying that it has been working in a "good faith effort" to develop and implement a safe reopening plan for the Tesla factory.
"We appreciate that our residents and businesses have made tremendous sacrifices and that together we have been able to save lives and protect community health in our region. We need to continue to work together so those sacrifices don’t go to waste and that we maintain our gains," Neetu Balram, the public information manager for the county's public health department said in a statement.
"It is our collective responsibility to move through the phases of reopening and loosening the restrictions of the Shelter-in-Place Order in the safest way possible, guided by data and science," Balram added.
Also on Saturday, Musk threatened to move Tesla's operations out of California and into "Texas/Nevada" in a since-deleted tweet, calling the reopening saga the "final straw," according to The Associated Press.