U.S. workplace safety regulators have announced more than $4 million in penalties on more than 300 employers they say put workers at risk during the COVID-19 pandemic.

But about two-thirds of these employers aren’t paying up.

Only 108 companies had paid a total of about $897,000 in fines as of last week to the Occupational Safety and Health Administration (OSHA) since the pandemic hit the United States last year.

Those who haven’t paid include meatpacking giants Smithfield Foods Inc and JBS USA – which had outbreaks infecting thousands of workers – as well as packaged foods company Conagra Brands Inc.

All three firms have appealed the citations and say they are without merit.