Smoke rises from a fire at a Coupang warehouse in Seo-gu, Incheon, on Sunday. (Yonhap) A fire at a Coupang logistics center in Incheon was still burning more than 24 hours after it broke out, as dense smoke, extreme heat and concerns over the building’s structural stability hampered firefighting efforts Sunday.The blaze began at 6:54 a.m. Saturday on the sixth floor of the fulfillment center in Seohae-gu, according to fire authorities. It later spread to the seventh floor through the building’s exterior wall.Thick black smoke engulfed the facility, which has a floor area of about 299,000 square meters.All 121 people inside the building evacuated safely. One firefighter was hospitalized for smoke inhalation. Another was treated for exhaustion and later discharged.Fire authorities issued a Level 1 response at 9:15 a.m. Saturday, and upgraded it to Level 2 at 12:25 p.m., expanding the operation to include personnel and equipment from five to six nearby fire stations.About three hours later, the National Fire Agency issued a national firefighting mobilization order, bringing in specialized equipment, including aerial ladder trucks and unmanned firefighting robots, from Seoul, Gyeonggi Province, the Chungcheong provinces and Gangwon Province.Despite the large operation, firefighters struggled to bring the blaze under control because of the large amount of combustible material stored inside the warehouse, which generated dense smoke and intense heat.Fire officials also detected signs that the building had weakened, including sections of the concrete ceiling falling inside the facility. Commanders temporarily withdrew firefighters from the building at around 6:50 a.m. Sunday over safety concerns.“Dense smoke and extreme heat continue to restrict visibility, making it difficult for firefighters to enter the building,” an official from the Incheon Fire Headquarters said.The official said crews had established firebreaks at several locations and were using excavators and forklifts to clear obstacles and prevent the fire from spreading.