On April 26, 1942 in the Benxihu (Honkeiko) Colliery (coal mine), what is believed to have been the world's worst mining disaster took place, killing 1,549 miners.[3] The disaster occurred in an area that is now within the bounds of modern-day China, but was then in a portion of China occupied by the Japanese, just north of present-day Korea. The Japanese administrators of the mine had the actual mining work performed by forced Chinese labor under harsh conditions. The disaster first began with a mine fire, but at the time, a hasty decision was made by the Japanese mine operators to promptly cut off the ventilation and to completely seal off the mine to kill the fire. This reportedly left many unevacuated workers still alive within the sealed-off area of the mine to eventually also suffocate. Once the fire was put out in this manner and the mine re-opened, it took 10 days to remove all of the bodies.[4] Of those killed, 1,518 were Chinese, and 31 were Japanese. Afterwards, several bodies were buried in a mass grave. According to a follow-up investigation carried out by the Soviet Union, the majority of the fatalities were not caused by the initial fire, but instead were the result of secondary carbon monoxide poisoning and suffocation.