Fire officials in the South Korean capital say a large blaze at a construction site near a 600-year-old palace has killed at least four workers and injured about 20. They say Gyeongbok palace wasn't damaged by Monday's fire, which filled Seoul's central district with smoke, according to a report of the Associated Press. Seoul Metropolitan Fire and Disaster official Kim Byung-ro says the workers died after inhaling toxic smoke. One of the injured is in critical condition. Kim says the blaze may have started when a spark from construction at the site of a national art museum landed in combustible material. About 170 firefighters extinguished the fire in about an hour.