Minnesota workplace safety regulators have received 159 coronavirus-related complaints since March 1. They opened 10 formal investigations, including three involving food-processing facilities.

Three of the 10 cases have been closed without any citations levied against the employers, according to the Minnesota Department of Labor and Industry, which includes the state’s Occupational Safety and Health Administration (OSHA).

Two of OSHA’s seven open COVID-19 investigations involve meatpackers that have been hit by outbreaks: the JBS pork facility in Worthington and the Pilgrim’s Pride chicken plant in Cold Spring. A third open case involves a vegetable cannery.

Other workplaces inspected by Minnesota OSHA for COVID-19 complaints are in several industries, including pipe fabrication, animal feed manufacturing and courier delivery service.

When initiating an OHSA investigation, “the department weighs a variety of factors, including, ‘Is this an isolated situation where the employer can quickly resolve the situation?’ ” said Labor and Industry Commissioner Nancy Leppink.

OSHA follows up with employers and workers to ensure a resolution sticks in such cases, she added. If not, an investigation could be launched. Investigations can be sparked by several issues, including if workers are in imminent danger or if they claim serious safety violations.

In addition to receiving outright complaints, the Labor and Industry Department has gotten a multitude of coronavirus queries from workers and employers. OSHA said its compliance staff has been tripled to respond to the calls for information and assistance.

Meatpacking plants have seen the largest workplace outbreaks of COVID-19 in Minnesota.

As of Thursday, 541 of the more than 2,000 JBS workers in Worthington had tested positive for COVID-19, by far the state’s biggest workplace outbreak, according to the Minnesota Department of Health.

The second-largest appears to be at Pilgrim’s Pride, which employs more than 1,100 in Cold Spring and had 83 COVID-19 cases as of Thursday, Health Department data show. Pilgrim’s Pride is majority-owned by Brazilian global meat giant JBS S.A.

The Department of Labor and Industry also has received 389 workers’ compensation claims where the suspected injury is COVID-19. It’s unknown yet whether these claims will be paid or denied, according to the department.

For most workers, “it can be quite difficult to establish that a communicable disease is caused by work,” Leppink said.

But the Legislature last month passed a law that should make it easier for certain employees to receive workers’ compensation, including nurses and certain other health care workers; police officer and firefighters; and correctional officers.

“They now have the presumption that they have an occupational disease compensable under workers’ compensation” if they test positive for COVID-19, Leppink said.

Normally, workers don’t have that presumption with a communicable disease, meaning they must bear the full burden of proof.