Ford temporarily suspended work at part of its Kansas City assembly plant Tueday after another employee tested positive for Covid-19. The shutdown in the Missouri plant lasted only an hour, and Ford completed its scheduled production for the day. But the closure is a sign of the difficulty of building cars while keeping workers safe from the Covid-19 pandemic. It is the third time that a Ford plant has had a temporary and partial suspension of work since it reopened its US plants on May 18. Most US auto plants were closed for nearly two months in response to the outbreak. “The safety of our workforce is our top priority,” said Ford in a statement. “In this instance, our protocol calls for us to deep clean and disinfect the employees’ work area, equipment, team area and the path that the employee took while at the plant.” The worker had been adding trim to the Transit van, one of two vehicles built at the plant along with the F-150 pickup. Most of the Transit assembly line continued to operate while the area was cleaned. The F-150 assembly line was not affected. Ford\n \n (F) rivals General Motors\n \n (GM) and Fiat Chrysler\n \n (FCAU) both confirmed Wednesday that employees at their plants have tested positive for Covid-19 since work resumed. But they said those instances did not require a suspension of work under the safety protocols they have in place. The response to each instance of a positive test is considered on a case-by-case basis, said GM spokesman Jim Cain. At Fiat Chrysler, once an employee tests postive for Covid-19, “our comprehensive, multi-layered safety measures of social distancing, mandatory use of personal protection equipment, and cleaning and disinfecting are in full use,” said Fiat Chrysler spokesperson Jodi Tinson. “These protocols are the most effective way we can create a safe and secure working environment for all of our employees.” Several nonunion automakers, including Volkwagen, Honda and Hyundai, said they have not had to shut their US plants since resuming work. Volkswagen said that two employees have tested positive for Covid-19 since it resumed production in Chattanooga, Tennessee, on May 17. Hyundai, said plant workers at its plant in Montgomery, Alabama who test positive did not return to work so its operations were not halted. The city of Montgomery has been hit hard by the pandemic in recent weeks. Virtually all auto plants around the globe were closed for an extended period due to the pandemic, but most have now resumed work. The three suspensions of work at Ford plants show that resuming production at auto plants will not be a smooth operation, said David Leggett, automotive analyst with GlobalData. “Vehicle makers across the world are facing similar issues as they restart manufacturing facilities that were shuttered during Covid-19 lockdowns,” he said. “Even while first wave Covid-19 infection peaks have been passed, the Covid-19 pandemic is far from over and fresh outbreaks can disrupt activity.” The Ford plant in Chicago, which shut down ast week after positive tests for two employees, had to close briefly a day later when one of its suppliers, Lear\n \n (LEA), had a positive test at its own plant. Ford also shut its Dearborn truck assembly plant last week after a worker tested positive there. “The supply chain is ultimately only as strong as its weakest link,” Leggett added. “Any disruptions to manufacturing companies along the supply chain anywhere in the world will impact others.” Car sales have fallen sharply in recent months, because of the record number of workers who have lost their jobs and million millions who are working from home and not commuting to work. That weaker demand for cars is another problem that automakers face from the Covid-19 pandemic, Leggett said.