Six persons died and one other fell sick on Tuesday after allegedly inhaling accumulated carbon dioxide inside an under-construction septic tank in Odisha’s Kalahandi district.Police reached the scene and an investigation is underway. (Representative Photo/iStock)The deceased were identified as Nimai Pal (48), owner of the house where the tank was being constructed, and his son Akash Pal (28), both residents of Karlakhunta village; Adal Majhi (55), Manoranjan Hati (27) of Matoganda village, and Chhanda Jal and Bipul Jal of Duta village.The incident took place in Karlakhunta village under Madanpur Rampur police limits when centring-related work on the septic tank was underway. Preliminary reports suggest the mishap occurred during the removal of centring materials from the tank, which may have contained toxic gases.According to the police, a worker first entered the tank but soon experienced breathing difficulties and failed to return. In an attempt to rescue him, six others entered the tank one after another.However, they too reportedly lost consciousness inside the confined space. Police suspect a case of suffocation caused by the build-up of carbon dioxide or other toxic gases.Also Read: ₹4 cr cash seized from mines official’s flat in record cash haul: Odisha VigilanceLocals later pulled the victims out of the tank and rushed them to the Madanpur Rampur Hospital, where doctors declared six of them dead on arrival.Pankaj Bhoi (32) of Hatikhoj village, fell sick and was initially admitted to Madanpur Rampur Hospital before being shifted to the District Headquarters Hospital as his condition deteriorated.Police reached the scene and an investigation is underway.While the exact cause of death is yet to be confirmed, preliminary findings indicate toxic gas accumulation inside the septic tank causing suffocation, police said. Kalahandi SP Nagaraj Devarkonda said exact reason of death will be known after post-mortem reports are receivedOfficers said confined spaces such as septic tanks are known to accumulate hazardous gases, including carbon dioxide, coupled with high humidity that caused workers to lose consciousness and die.Expressing grief over the deaths, chief minister Mohan Charan Majhi announced an ex gratia of ₹4 lakh each for the next of kin of the deceased.