Michigan Gov. Gretchen Whitmer warned Wednesday that the state’s auto factories could be shut down again if residents don’t follow her order to wear masks and slow the spread of the coronavirus.

“If Michiganders don’t mask up when we go out in public, cases could rise and we could be forced to close down more of our businesses, including auto manufacturing plants that employ thousands,” Whitmer said at a press conference in Lansing, Mich. “A second wave of this virus could be absolutely devastating.”

The warning comes as automakers crank up output at factories to try to meet surprisingly strong demand, especially for pickups, crossovers and SUVs. General Motors, Ford Motor Co. and Fiat Chrysler Automobiles temporarily shuttered factories in Michigan and elsewhere in the U.S. in March to help control the COVID-19 outbreak.

Whitmer cleared the way for those plants to reopen in May amid signs the pandemic was receding in the state.

Among automakers dependent on Michigan factories, Ford has a lot riding on local production of the redesigned and top-selling F-150 pickup and revived Bronco SUV after a quarter century hiatus. The Ford Ranger pickup, one of just two Ford Motor Co. nameplates to post a year-over-year gain in second-quarter sales, is also produced in Michigan.

GM is running its plants full out to replenish truck inventories. Other popular models built in Michigan include the Ram pickup, Jeep Grand Cherokee and Chevrolet Traverse.

On Wednesday, Michigan reported 891 new cases of COVID-19, the most daily new cases since May 14. That brings Michigan’s total number of cases to 71,197. The state says 6,085 residents have died of the disease.