DETROIT, Michigan: Detroit's three big automakers - General Motors, Ford and Chrysler parent Stellantis NV - have announced that wearing face masks will be optional for workers at their U.S. facilities.

In mid-May, the Detroit automakers and the United Auto Workers, which launched a COVID-19 joint task force, reinstated a requirement for employees to wear masks in southeastern Michigan during a COVID-19 surge.

This week, however, the task force stressed that it "strongly recommends masking" if a facility is in a high-risk county, as identified by the Center for Disease Control, but that mask requirements will no longer be mandatory.

The change was effective immediately, GM said.

In early March, the automakers said workers would not need to wear masks at workplaces deemed safe by U.S. health officials.

In February, CDC masking guidelines shifted from a focus on the rate of COVID-19 transmission to monitoring local hospitalizations, hospital capacity and infection rates.

Also, the automakers did not mandate that U.S. employees become vaccinated, but recommended workers do so.