At least four factory workers are dead, and another four have been injured. Casualties were taken to a local hospital following the Friday morning explosion in Yeosu, Yonhap reported.
It was previously reported that only three of the eight workers were believed to be dead.
Responding authorities believe the Yeochun NCC Co. factory explosion took place during a test of the factory's heat exchange system.
The official cause of the incident remains under investigation.
Yeochun NCC, also known as YNCC, manufactures and sells a number of important and highly-toxic industrial chemical products, including benzene, propylene, ethylene, toluene, xylene and styrene monomer.