It took only two days for a reopened Ford assembly plant to grind to a halt over the coronavirus.

Thousands of workers at Ford’s facility in Chicago were forced to leave the site Tuesday on just the second day of operations after two workers tested positive for COVID-19 — and a second company factory in Michigan had to close for the same reason on Wednesday, CNN reported.

The departures came after the American automaker began bringing back 12,000 North American workers the day before. Ford promised a slew of safety-related changes included social-distancing reminders, reconfigured workspaces and temperature checks.

Some employees told the local CBS affiliate they were grateful to be able to work and earn a living, though others still feared for their safety.

“I’m worried right now,” said employee Timothy Shy. “This is the second day, and we are already hearing about this.”

Another employee, Billy Cowart, added “social distancing doesn’t really work.”

The Chicago plant builds the Ford Explorer, the Lincoln Aviator and the Ford Interceptor police car. Workers there returned to work for the second time on Wednesday morning, CNN reported.

But by that time, a second Ford facility in Dearborn, Michigan, where the F-150 pickup is produced, also shut down after a worker there tested positive, according to the outlet.

The brief closures demonstrate the difficulties facing major American manufacturers looking to ramp up operations as states begin to reopen. Ford’s factories had been shut down for two months during the pandemic.

“There are three things that have to all come together. You have to have a healthy work force, a healthy supply chain and healthy demand,” Kristin Dziczek, vice president of industry, labor & economics at the Center for Automotive Research, told CNN. “It’s not just flip a switch and everything is as it was. It’s very complicated.”

Ford did not immediately respond to a request for comment, though a spokesperson told CNN the company believed the workers contracted the virus before returning to the factories.

“When two employees who returned to work this week tested positive for COVID-19, we immediately notified people known to have been in close contact with the infected individuals and asked them to self-quarantine for 14 days,” said Ford’s spokesperson, Kelli Felker.

“We also deep cleaned and disinfected the work area, equipment, team area and the path that the team member took.”