The man was pronounced dead at the scene after Whittier police received a 911 call at 7 a.m. Thursday.
Jose Melena, 62, had worked for six years at tuna maker Bumble Bee Seafoods.
An initial investigation indicated that Melena was fatally injured when he was cooked in an oven, according to Erika Monterroza of California Division of Occupational Safety and Health.
It was unclear how Melena ended up inside the industrial cooker, which was described as a "steamer machine."
The seafood plant had shut down but was expected to resume operations Monday, according to a statement from Bumble Bee Foods.
"The entire Bumble Bee Foods family is saddened by the tragic loss of our colleague, and our thoughts and prayers are with the Melena family," said Pat Menke, Bumble Bee Foods vice president of human resources, in the statement.
An investigation from Cal-OSHA will be completed within six months. The investigation will include visits to the plant, extensive interviews and a review of company safety documentation, according to state policy.
A finding of violations could result in civil penalties -- and possible criminal charges.
