An auto battery factory in the southern city of Cheongju caught fire Friday, leaving one person trapped inside.
Firefighters said an explosion is believed to have sparked the blaze that broke out at the factory around 3 p.m.
Two people were immediately rescued, but one other is still inside the building, according to authorities.
Dozens of fire trucks and firefighters were dispatched to put out the flames.
Authorities said rescue efforts were being hampered by plumes of black smoke engulfing the factory.