The closure comes about a month after President Donald Trump issued an executive order for meat processing plants to stay open despite virus outbreaks at several slaughterhouses. Those outbreaks led to the closure of around 20 plants in April, Reuters reported.

Tyson Foods announced the closure late Thursday, hours after the Iowa Department of Public Health (IDPH) had confirmed 555 coronavirus cases at the plant out of a workforce of 2,517, the Des Moines Register reported.

"I honestly feel like the company has failed its employees," Storm Lake League of United Latin American Citizens of Iowa Vice President Mayra Lopez told the Des Moines Register. "With 555 cases confirmed, that seems pretty steep."

Lopez, who has friends and family among the plant's many minority workers, said that she had heard of employees waiting up to a week for coronavirus test results.

"By the time they get the results, it could be too late and they've passed it on to someone else," she said.

Tyson Foods said that the closure was due to a delay in testing results and the absence of employees due to quarantine. It said it would stop slaughtering and finish all processing over the next two days.

"Additional deep cleaning and sanitizing of the entire facility will be conducted before resuming operations later next week," the company said in a press release reported by the Des Moines Register.

The incident has added to concerns about employee safety in meatpacking plants forced to remain open despite the fact that crowded working conditions make social distancing difficult. Tyson said it implemented wide scale testing at the Storm Lake plant and required employees to wear masks, but the United Food and Commercial Workers International Union (UFCW) said that meat companies and the Trump administration could do more to protect workers, Reuters reported. More than 3,000 U.S. meatpacking workers have tested positive for COVID-19 and 44 have died, the union said.

"Too many workers are being sent back into meatpacking plants without adequate protections in place, reigniting more outbreaks in the plants and our communities," Nick Nemec, a South Dakota farmer who is part of an advocacy group that works with UFCW, told Reuters.

Previously, coronavirus outbreaks had forced Tyson Foods to shutter plants in Waterloo, Columbus Junction, and Perry, Iowa, as well as in Dakota City, Nebraska; Logansport, Indiana; and Pasco, Washington, according to the Des Moines Register. However, most of those plants have since reopened, The Hill reported.

In April, Tyson Chairman John Tyson warned that "the food supply chain is breaking." The warning preceded Trump's executive order by two days.

However, a recent Food and Water Watch report has cast doubt on industry claims of shortages. It found that the U.S. Department of Agriculture (USDA) reported that cold storage of beef, pork, chicken and turkey was up 2.1 percent in April 2020 compared with April 2019. Further, meat exports have been on the rise in May.

At the same time, plants have persisted in switching to the New Swine Inspection System, which allows fewer inspectors and faster slaughter speeds. Plants that have switched to this system have seen increased coronavirus cases. One such plant in Guymon, Oklahoma reported 440 cases, the most in the state.

"The USDA itself is showing that industry claims of impending food shortages are hogwash — meat exports are actually increasing and cold storage stockpiles of meat are growing. Meanwhile, the numbers of workers in deregulated plants are proving for us the importance of meat slaughter line speed caps and federal meat inspection," senior government affairs representative for Food & Water Action Tony Corbo said in a statement. "USDA should take a long, hard look in the mirror and reverse course immediately by forcing industry to cap line speeds, follow federal inspection guidelines, mandate worker safety protocols, and keep plants closed as long as necessary to prevent the spread of COVID-19."