TOKYO (REUTERS) - Japan's Mitsui Chemicals Inc said it shut the toner binder resin manufacturing unit at its Mobara branch factory in Chiba on Thursday (July 27) after a fire that injured four workers. A dangerous substance exploded and caught fire in a warehouse at the plant, located east of Tokyo, shortly after 11am (10am Singapore time), the local fire department said. Mitsui Chemicals said the fire occurred in a facility that makes toner binder resin and added that it was not clear what caused the fire. Four workers were burned but the injuries were not life threatening, a Mitsui Chemicals spokesman said, adding there was no impact to the operations of other product units at the factory. The fire was beginning to subside, he added. The factory makes chemical products such as formaline, acrylamide and unsaturated polyesters, according to the company's website. This story is developing