Things aren’t all going to plan for Ford, which restarted production at its North American facilities on May 18 after shutting them down due to the Covid-19 pandemic. Barely had production resumed that the automaker was forced to close two of its assembly plants earlier this week, Reuters reports.

The company closed its Dearborn, Michigan factory on Tuesday due to a positive Covid-19 test by one worker, but production was set to resume the following day. The plant builds the F-150 pick-up truck.

Its Chicago assembly plant, meanwhile, was closed due to shortage of parts. The plant, which assembles the Explorer and Lincoln Aviator SUVs, was also closed the day before when two workers on different shifts also tested positive.

While the company did not indicate the source of the parts shortfall, a person familiar with the matter told the news agency that Lear Corporation, which supplies automotive seating and electrical systems, had closed a plant in Hammond, Indiana, due to a positive test. Ford said that production in Chicago was also set to resume mid-week.

Not all of the Blue Oval’s production facilities have resumed. Earlier this month, the company had indicated that its Flat Rock Assembly Plant and Oakville Assembly Complex would only restart production from the week of May 25 on one shift.

The company has put in place a series of protocols and practices that all employees must follow. These include daily online health self-certifications before work, temperature scans upon arrival, mandatory use of face masks and shields, social distancing and more time between production shifts to limit interaction and allow for additional cleaning.