Two workers died Monday after collapsing in an underground conduit at a waste material processing facility in Izumi, Osaka Prefecture, police said.
The victims were identified as Hisatoshi Yamasaki, 48, and Takashi Takegoshi, 68.
According to the initial investigation, one of the men complained of feeling sick before collapsing at around 4 p.m. while replacing parts in the conduit.The second man collapsed after entering the conduit to rescue him.
The police suspect some form of toxic gas was responsible for their deaths.