The blaze at the unfinished four-storey warehouse site in Icheon on Wednesday, 80km (50 miles) southeast of Seoul, spread “extremely quickly” and rendered those inside “unable to evacuate”, South Korea’s Yonhap news agency reported citing fire officials.
Eight of the injured were in a serious condition, local officials said. Firefighters said the blaze started on the second underground level, Yonhap reported.
Witnesses said they heard at least 10 explosions.
President Moon Jae-in ordered government officials to mobilise all available resources in the search and rescue effort, Blue House spokesman Kang Min-seok said.