Six workers and two local residents were taken to hospital Thursday after inhaling gas at a fertilizer factory in Wakayama, police and municipal officials said.
Three of the eight are in serious condition, and the heart and lungs of one of the workers have already failed, according to hospital officials.
Police said the workers were apparently hit by hypoxia, a deficiency of oxygen, after they inhaled gas emitted while they were heating wool for processing. The gas has not been identified.
An unusual odor was detected in and around the factory in the prefectural capital when rescuers rushed to the site in response to an emergency call at around 2:05 p.m., municipal officials said.
Nearby residents said they are experiencing throat and eye pain, police said.
The plant is located in a district of southern Wakayama dotted with factories. According to investigators, the factory in question not only processed wool but also turned leather scraps into fertilizer.