GREEN BAY - Federal regulators will investigate Green Bay meatpacking plants hit hard by the coronavirus even as Brown County officials assert the companies are following proper health protocols.

A spokeswoman for U.S. Occupational Safety and Health Administration said Friday that the agency is looking into JBS Packerland and American Foods Group in Green Bay after cases of COVID-19, the disease caused by the virus, exploded at both companies.

OSHA will inspect the JBS plant, located on Lime Kiln Road. The agency is also responding to complaints at American Foods facilities on University Avenue and Acme Street.

News of the investigations came as the number of Brown County cases surged to 618 Friday, an increase of over 100 from the previous day. Six people in the Oneida Nation are also sick, and 23 county residents are hospitalized.

Brown County now has by far the highest rate of tests coming back positive for COVID-19 among Wisconsin's 72 counties. Twenty-six percent of the 2,291 people tested in Brown have been found to be infected. Milwaukee County is next at 17% and Kenosha County is third at 16%.

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County health officials as of Friday had traced 189 cases to JBS, 75 to American Foods and 23 to Salm Partners, a sausage manufacturer in Denmark. The numbers for JBS and Salm were the same as those reported Thursday, while American Foods was linked to 20 additional COVID-19 infections.

Claire Paprocki of Brown County Health and Human Services said the department still hasn't found evidence linking the recent spike to the April 7 election, which forced some Green Bay voters to stand in line for hours at two consolidated polling locations.

Investigators ask potential COVID-19 patients if and how they voted and if they worked at the polls, she said.

County says plants are safe

Paprocki said county and state health officials, along with the Centers for Disease Control and Prevention, determined that the meat-processing facilities are adhering to public health guidelines and social distancing. The companies are now also testing employees.

"All three facilities are following guidance properly to assure that the workplace is safe for employees," Paprocki said.

Salm Partners said in a statement Friday that it's offering free testing to as many of the company's 500 employees who want it, in order to keep employees safe. The company is not requiring workers to be tested, but will pay workers who choose to be tested for an extra hour of work, a spokeswoman said.

She said the 23 positive tests linked to Salm include 11 employees, and that nine of the 11 have returned to work. None is believed to have become ill while at work.

A JBS spokesman previously said the company is ramping up sanitation efforts, staggering breaks and lunch periods, and requiring sick employees to stay home from work. JBS also ordered masks and thermometers in March and required masks to be used company-wide on April 13.

Dr. Paul Casey, an emergency physician with Bellin Hospital, said testing of JBS employees began Monday as they arrived for work. Roughly 50 JBS workers were sent home Monday because they exhibited COVID-19 symptoms, he said. Approximately 30 more were sent home on Tuesday.

Testing was done in a medical tent set up outside the plant over the weekend, Casey said.

Representatives from American Foods have failed to address the Press-Gazette's questions all week.

Worker advocates contend the companies also have failed to protect employees and that current efforts are too little, too late.

Voces de la Frontera, a Milwaukee-based worker rights group, filed complaints about JBS and American Foods to OSHA on April 13, according to records obtained by the Press-Gazette. Voces demanded that both companies provide masks, ensure employees can practice social distancing and inform workers about positive cases.

The organization also asked JBS and American Foods to provide workers with paid sick leave.

At the time of Voces' letter, JBS had one confirmed case, "rumors of a second" and pending test results, the letter states. Five employees at American Foods were also reportedly sick as of April 13 — four at the main plant and one at the Acme Street facility.

OSHA told JBS and American Foods they had until Thursday to investigate the allegations and report back with their findings, documents show.

The OSHA spokeswoman declined to provide further details about the investigations until they are complete.

Contact Haley BeMiller and Doug Schneider at hbemiller@gannett.com and dschneid@gannett.com. Follow them on Twitter at @haleybemiller and @PGDougSchneider.