Kroger stores. Photo via CBS News Kroger and Costco are among the big U.S. supermarket chains now limiting how much ground beef and fresh pork customers may buy amid escalating concerns about meat supplies in the U.S. Their moves follow shopper limits announced last Friday by Kroger, the nation’s largest supermarket chain. Kroger cited the rash of closures at meat processing plants in multiple states due to outbreaks of COVID-19 among workers at the facilities, according to an email the company sent to CBS MoneyWatch. First reported by CNN, Kroger did not reveal how many of its locations would be curbing customer purchases of beef and pork. Kroger operates more than 2,700 stores under multiple banner names, including Fred Meyer and Harris Teeter. “At Kroger, we feel good about our ability to maintain a broad assortment of meat and seafood for our customers because we purchase protein from a diverse network of suppliers,” a spokesperson said in the email. “There is plenty of protein in the supply chain; however, some processors are experiencing challenges.” Kroger is not alone in restricting how much protein consumers can pile into their shopping carts. Warehouse chain Costco is also temporarily restricting purchases of beef, pork and poultry products, limited to three items per member. “Costco has implemented limits on certain items to help ensure more members are able to purchase merchandise they want and need. Our buyers and suppliers are working hard to provide essential, high demand merchandise as well as everyday favorites,” it stated on its website. And Giant Eagle stated on its website: “To ensure availability of popular items including ground beef and on-sale meat items, we are temporarily limiting the purchase amount of these items to two of each per transaction.” More than 20 meatpacking plants around the U.S. have closed at some point in the past two months, reducing pork production by about a quarter and cutting beef output by about 10%, according to the United Food and Commercial Workers, a trade union. Nearly 4,200 workers at 115 meatpacking plants have been infected with the coronavirus, and 20 of those workers have died, according to a report released Friday by the U.S. Centers for Disease Control and Prevention. The CDC findings likely underestimate the scope of the problem as not all states with infections at meat plants have reported them to the federal agency. — CBS News’ Max Bayer contributed to this story. First published on May 1, 2020 / 6:35 PM © 2020 CBS Interactive Inc.. All Rights Reserved.