Manufacturing workers have expressed concern about returning to plants amid the pandemic.

The United Auto Workers union, which represents employees at General Motors, Ford Motor Company, and Fiat Chrysler, deemed the proposed timeline of reopening in early May premature, leading to long negotiations over safety protocols.

Companies have to assure workers that it is safe to return as well as comply with federal and state guidelines, which often require redesigning work stations and plant floors.

While large automakers have valuable experience on updated manufacturing processes from plants in other countries, small U.S. manufacturers are making these changes for the first time. Experts contend more guidance is needed from the government.