BHUBANESWAR: At least three people were killed after inhaling poisonous carbon monoxide gas in a sponge iron factory in Orissa's Jharsuguda district, police said Friday. The deaths occurred at the Singhal Enterprises Private Ltd. factory at Hirma, some 400 km from here, at around 8 p.m. Thursday. Inspector in charge of the local police station P.K. Rout told IANS on phone that the three men aged between 22 to 25 years had gone to wash a chamber used to cool hot sponge iron and got trapped inside. They died of suffocation after inhaling carbon monoxide.