A fourth worker involved in the June 29 accident at Tampa Electric's Big Bend Power station died Saturday at Tampa General Hospital, the Hillsborough County Sheriff's Office said.
Frank Lee Jones, 55, succumbed to his injuries around 5 p.m.
His son, Frankie Atkins, confirmed the death.
In a video message released late Saturday, Tampa Electric CEO Gordon Gillette said he was saddened to report the death toll had risen to four.
"This was a horrible accident and I am deeply saddened by its very human impact," he said.
Gillette thanked the community for its support and added: "I'm sorry to acknowledge the obvious: that this incident and its aftermath are far from over."
Jones was one of six workers who were severely burned when molten slag gushed out of a tank at the Apollo Beach power plant. The substance can reach temperatures of more than 1,000 degrees.
Senior plant operator Michael McCort, 60, and contract worker Christopher Irvin, 40, died at the scene.
Contract worker Antonio "Marro" Navarrete, 21, died Wednesday.
Two others remained in the hospital late Saturday: Jones' stepson Gary Marine Jr., 32, and Armando J. Perez, 56.
Jones was a contract worker employed by Gaffin Industrial Services in Riverview. He had been with the company for 27 years.
Atkins, his son, worked with him for a time, but Jones made him find another job because the work was too dangerous.
In the immediate aftermath of the accident, Atkins told the Tampa Bay Times that Jones was a family man who did everything he could to support his kids.
Contact Melissa Gomez at firstname.lastname@example.org. Follow @melissagomez004.