In late June, five workers at TECO's Big Bend power station in Apollo Beach were gravely injured in an accident.
Two died that day, three others later succumbed to their injuries. Another worker was left seriously burned.
The explosion happened when the workers were trying to unclog a blockage in a tank of molten coal that's burned to generate electricity.
Scott Balfour, the Chief Operating Officer of Emera, the Canadian power company that owns Tampa's TECO Energy, said during a quarterly shareholder conference call that investigations, both internally and by the U.S. Occupational Safety and Health Administration, are ongoing and expected to take several months.
"Until those investigations are complete, we will not know for certain, nor will we be able to comment on, the causes,” Balfour said.
Tampa Electric has created a relief fund to raise money for the victims and their families.