Tyson Foods fired seven managers at its Waterloo, Iowa, pork processing plant
The firings followed an independent investigation confirming allegations they bet on the number of workers that would test positive for COVID
The lawsuit was filed on behalf of four plant workers who died from coronavirus
Five of the seven fired plant managers have been named in the lawsuit
Former night manager Don Merschbrock, who was not named in the suit, said the office betting pool was meant to be a 'morale boost'
He said he didn't believe that the cash pool had violated company policy
County officials said last May that more than 1,000 workers had tested positive