A tragic accident at an under-construction septic tank in Odisha’s Kalahandi district claimed at least six lives on Tuesday (May 26) morning, with police suspecting that the victims died after inhaling toxic gases trapped inside the structure.

The incident took place at Gaud Karlakhunta village, triggering a rescue operation involving local residents, police and fire service personnel.

According to officials, the victims had entered the septic tank to remove centring materials from the under-construction structure when the mishap occurred. Among those who died were a father-son duo — Nimai Pal, 48, and Akash, 27 — at whose residence the septic tank was being built. The other deceased included three masons and a worker.

Police said the workers appear to have inhaled toxic gases accumulated inside the structure. A person who fell sick has been rushed to the hospital, where his condition is learnt to be serious, The Indian Express reported.

A police officer said a worker first entered the tank but failed to return, as he might have collapsed due to breathing difficulties. Six others then entered the tank one after the other, but lost consciousness.

Locals, police and fire service personnel launched a rescue operation and recovered the bodies from the under-construction septic tank, taking them to a nearby medical facility.

Police said they have registered an unnatural death case.

“The septic tank was constructed three weeks ago. Toxic gas might have accumulated because of excess heat. The collapse of centring material might have also led to some peoples’ death. We are waiting for the post-mortem report,” a police officer told The Indian Express.

Following the incident, Mohan Charan Majhi announced an ex gratia of Rs 4 lakh for the next of kin of each deceased person. The incident has once again drawn attention to the lack of safety measures and hazardous working conditions faced by labourers involved in construction-related work.