The Los Angeles district attorney said the company, its plant operations director and its former safety manager were each charged Monday with three counts of violating Occupational Safety & Health Administration rules causing death.
Prosecutors say Jose Melena was cleaning a 35-foot-long oven at the company's Sante Fe Springs plant in 2012 when co-workers loaded it with 12,000 pounds of tuna and turned it on.
Temperatures in the oven reached 270 degrees during the two-hour process.
The state's occupational safety agency previously cited the San Diego-based company with violations for failing to properly assess the danger to employees working in large ovens.