A boiler tower collapsed at a thermal power plant in the southeastern city of Ulsan, South Korea, on Thursday, trapping an estimated seven people.

Axar.az informs, ciitng Yonhap, the collapse was reported at the Ulsan branch of Korea East-West Power Co., a state-run utility company, shortly after 2 p.m.

Firefighting officials said two people were spotted under the structure and an operation was under way to rescue them. It was not immediately clear whether they were among the seven reported missing.

Two other people were rescued early on and were not in life-threatening condition, they said.

The collapsed tower was 60 meters tall and reportedly in the process of being dismantled using explosives. The trapped people are all presumed to be employees of a subcontractor.