At least six workers were killed and several others injured in a blast at a sponge iron factory in Chhattisgarh's Balodabazar- Bhatapara district on Thursday, officials said. The incident occurred at the Real Ispat Sponge Iron Factory located in Bakulahi village in the Bhatapara rural area, a police official said. After being alerted, police and senior administrative officials rushed to the spot and initiated relief and rescue operations, he said.