The fire, which has largely been extinguished, ripped through a factory run by battery manufacturer Aricell in Hwaseong, a major industrial cluster about 90 minutes southwest of the capital Seoul, Reuters reported.
The blaze began after a series of battery cells exploded inside a warehouse with some 35,000 units, said Kim Jin-young, a local fire official. What had triggered the explosion remains unclear, he added.
Yonhap news agency had earlier reported that some 20 bodies had been found inside the plant, but Kim told a televised briefing that 16 people had died and two others were suffering from burns and other serious injuries.
He said rescuers were inside the factory trying to find the five people unaccounted for.
SD/PR