Rescue officials search for three trapped workers at a library construction site in Gwangju, Thursday. (Yonhap)
Rescue officials search for three trapped workers at a library construction site in Gwangju, Thursday. (Yonhap)

A steel structure collapsed at a library construction site in the southwestern city of Gwangju on Thursday, killing two workers and trapping two 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.

Firefighters spotted the second victim, who remained unresponsive, earlier in the day, before finally rescuing him at 8:13 p.m., according to officials.

He was pronounced dead on site, with officials working to figure out the identity of the victim.

Two others are still unaccounted for, officials said, adding they plan to continue search operations overnight.

The four victims were identified as technicians affiliated with a subcontractor, with all of them being Korean nationals.

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.

The library under construction was being built by the Gwangju metropolitan government on the site of a former waste incineration plant.

The 51.6 billion-won ($35 million) project was being built to cover a total floor area of 11,286 square meters across two stories above ground and two floors in the basement. (Yonhap)