As two departments opened at the Sioux Falls plant operated by Smithfield Foods, employees filed through a tent where they were screened for fever and other signs of COVID-19.
Some said they felt Smithfield would protect their safety with measures aimed at preventing another virus outbreak, while others said they were not confident that infections could be halted in a crowded plant.
Lydia Toby, who works in the ground seasoned pork department, said she was "kind of worried" as she entered the plant before 6 am for her first shift in over two weeks.
The company met employees in her department Friday and explained they had installed dividers on the production line and would require everyone to wear masks.
"I think it's going to be OK," she said.
In the wake of an executive order from President Donald Trump ordering meat plants to remain open, Arkansas-based Tyson Foods was also resuming "limited production" Monday at its pork processing plant in Logansport, Indiana, where nearly 900 employees had tested positive.
And the JBS pork plant in Worthington, Minnesota - just an hour east of Smithfield's South Dakota plant - planned a partial reopening on Wednesday.
Virginia-based Smithfield is offering COVID-19 testing to all employees and their family members, according to a text message sent to employees and seen by The Associated Press.
The message told employees to report to a local high school to be tested.
It wasn't clear if testing was required before employees could return, and Smithfield didn't immediately respond to questions.
About 250 employees were told to report to work on Monday, according to the union that represents them. The plant employees about 3,700 workers and produces roughly 5 per cent of the nation's pork.
Salaheldin Ahmed, who works in a department that has not yet reopened, said he was called in by plant management to look at the changes that have been made in the plant.
"They fixed a lot of things," he said, describing how workers would be spread apart where possible.
According to a CDC report released Friday, more than 4,900 workers at meat and poultry processing facilities have been diagnosed with the coronavirus, including 20 who died.
Some states didn't provide data, so the actual count is believed to be higher.
The actual number of COVID-19 infections is also thought to be far higher than the number of confirmed because many people have not been tested and studies suggest people can be infected without feeling sick.
The CDC researchers said plant workers may be at risk for a number of reasons, including difficulties with physical distancing and hygiene and crowded living and transportation conditions.
They suggested that disinfection be enhanced and that workers get regular screening for the virus, more space from co-workers and training materials in their native languages.
The United Food and Commercial Workers union, which represents roughly 80 per cent of beef and pork workers and 33% of poultry workers nationwide, has called for stricter measures than CDC recommendations, including mandating that workers be spaced six feet apart on production lines.
It has appealed to governors for help enforcing worker safety rules. The union also want to get rid of waivers that allow some plants to operate at faster speeds.
As plants warily reopen or others operate at diminished capacity with many workers staying home sick or in fear, it's unclear Trump's order will guarantee an unbroken supply of meat in grocery store coolers.
It appeared it will take some time before meatpackers are able to both protect employees and operate at capacity.
Toby said that after reporting for her shift, she was told she was not needed and to come back on Tuesday. (AP) RUP