SEOUL, South Korea (AP) — 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.

South Korea Fire

Police officers carry an injured victim of a fire at the construction site after the fire broke out at a national art museum in Seoul, South Korea, Monday. Pic: AP.

They say Gyeongbok palace wasn’t damaged by Monday’s fire, which filled Seoul’s central district with smoke.

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 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.

In 2008, an arsonist destroyed a gate in Seoul regarded as a South Korean national treasure. It’s now being rebuilt.