A massive fire broke out at the assembly plant for a car battery manufacturer in Cheongju, North Chungcheong Province on Friday, prompting emergency operations by anti-fire authorities. 

According to an official, the factory run by battery maker Ecoprobm, located in Cheongwon District in Cheongju was engulfed in blaze after around 3 p.m. 

The official said four people were inside the facility at the time and three of them were rescued but the remaining employee is presumed to be still trapped inside the burning structure. 

An unidentified explosion was said to have caused the fire but a further investigation is underway. 

With the Grade Two response system put in place less than an hour after the fire broke out, some 100 firefighters and 33 fire trucks were mobilized to douse the blaze and search for the person who is presumed missing.