They were descendants of Koreans who moved to Northeast China, fleeing Japan’s brutal colonial rule in the early 20th century. In a twist of history, many like them have come to South Korea in recent decades, looking for better-paying jobs in their forebears’ homeland, now one of the world’s richest countries.

For more than a dozen of them, their Korean dream came to a horrifying end on Monday, when a toxic inferno engulfed a lithium-battery factory where they had found work. The 23 laborers killed in the plant in Hwaseong, a city south of Seoul, included 12 women and five men from China, ranging in age from 23 to 48, officials said. Most were ethnic Koreans…

The factory in Hwaseong was operated by Aricell, a small company that supplies batteries for South Korea’s military and other customers…

The walls of Building No. 3 were built with thin metal plates with plastic insulation — highly vulnerable to fire — in between them, Mr. Lee said. The factory also kept combustible materials near an exit door of the second floor, another safety lapse, fire department officials said…

Park Sun-gwan, the head of Aricell, apologized for the deaths on Tuesday. But he denied that his factory lacked safety measures, adding that it had trained its workers…