A steel structure collapsed at a library construction site in the southwestern city of Gwangju on Thursday, killing one worker and trapping three others, authorities said.
The accident was reported at 1:58 p.m., prompting firefighters to respond to the scene where they rescued a 47-year-old worker, who was taken to a hospital in cardiac arrest but later pronounced dead.
A second worker's location was identified and an operation was under way to rescue him, while two others were yet unaccounted for.
Firefighting officials said the structure appeared to have collapsed while ready-mixed concrete was being poured.
A construction site official told Yonhap News Agency the rooftop of the second floor appeared to have collapsed down to the first floor, with no supports installed in between.
