The fire broke out in the COVID-19 intensive care unit of the SANKO University Hospital on Saturday after a high-flow oxygen therapy machine used in the treatment of COVID-19 patients had exploded.
At the same time, seven hospital workers who was injured while trying to save patients are also receiving treatment.
Other coronavirus patients receiving treatment in the unit were transferred to nearby hospitals.
The victims aged between 65 and 85, a statement by the university said.
The investigation that has been launched into the deadly incident continues.