Face masks, once thought of as an unnecessary precaution for healthy people during the novel coronavirus pandemic, are now being mandated in cities and counties across the United States.

Late last week, the federal government reversed its previous position on face coverings, issuing guidance that urges people to wear them in public places. President Trump stopped short of saying it should be required, but some local officials have taken enforcement into their own hands.

Los Angeles Mayor Eric Garcetti on Tuesday ordered all residents to wear face coverings when visiting grocery stories, pharmacies and other essential businesses, as well as when entering ride-booking vehicles. This law is enforceable with a fine, imprisonment or both. The city of Miami has issued a similar order.

And closer to the nation’s capital, Montgomery County, a suburb of 1 million, announced Thursday that all shoppers must wear face coverings in grocery stores, pharmacies and other retail establishments starting Monday.

Under the order from county health officer Travis Gayles, businesses must also limit the number of customers in the store and enforce social distancing among patrons while they wait. Those who fail to do so could face a $500 fine, the county said in a statement.

The new requirements in Montgomery come just one day after D.C. Mayor Muriel E. Bowser (D) issued a similar order on social distancing and masks for patrons shopping for food.

It also comes after the Montgomery County Council announced plans to consider a regulation that would have mandated face coverings in essential businesses by April 23.

County Council member Hans Riemer (D-At Large) said that in light of Gayles’s order, council members do not intend to pursue further regulation.

“Good news,” he said. “Now we have a nice, strong policy — and earlier than we wanted.”

Officials say a mask mandate is necessary in Montgomery, which has been designated a hot spot for the virus with more than 1,200 known infections and 29 deaths as of Thursday morning. Others warn that it may be difficult for businesses and residents to comply within the short time frame given that masks — even cloth ones — are in short supply.

This week, major supermarket chains began to report their first coronavirus-related deaths. In Prince George’s County, a 27-year-old employee at the Giant supermarket in Largo last week became the region’s youngest coronavirus fatality.

Jupiter Pastor, a manager at local grocery store Grosvenor Market, said about five of his employees have stopped coming in for shifts, fearful of contracting the virus.

“They’re scared; they don’t want to bring it home,” he said. “Who can blame them?”

Pastor said Wednesday that a county-enforced mandate on facial coverings would be “awesome.” All employees at Grosvenor started wearing masks and gloves two weeks ago, and customers who enter the 8,000-square-foot store are asked to use plastic gloves when handling produce.

Clark Construction, headquartered in Bethesda, said it has procured cloth masks for all employees and is in the process of distributing them to job sites across the country. Safeway, which has 1,559 employees in Montgomery, said reusable and disposable masks are being transported to all front-line associates at its grocery stores.

Montgomery County Executive Marc Elrich (D) said Tuesday that he was “not opposed” to regulation but is unsure whether it would be plausible for every resident to procure masks.

“Even the hospitals are struggling,” he said.

Garcetti said when announcing his order in Los Angeles that he waited to introduce the mandate until he was confident that there was an adequate supply of cloth masks in the city.

“Our capacity, thanks to the amazing apparel industry here, has expanded, and people can buy them online,” he said.

Riemer noted that the Centers for Disease Control and Prevention has issued guidance on how to make cloth masks at home out of T-shirts and hair ties, adding, “This is not something that requires money or effort. . . . It’s not difficult to do.”

To ensure that low-income residents can comply with the order, Riemer said, he plans to propose an appropriation of $1 million for the county to buy cloth masks in bulk to be distributed to residents through the county’s nonprofits.

Following the new federal guidelines on face coverings, some black Americans expressed concern that covering their faces may cause them to be treated with suspicion.

County Council member Will Jawando (D-At Large) said he is concerned that the enforcement of this mandate may create opportunities for racial profiling. In Illinois, two black men said in March that they were kicked out of a Walmart for wearing protective masks.

“We need carrots, not sticks,” said Jawando, one of two council members who did not co-sponsor the regulation, along with Andrew Friedson (D-District 1).