Three workers working in a newly-constructed septic tank and a passerby who had attempted to rescue them died of suffocation at Padalaguda village in Nabarangpur district on Tuesday.

The deceased have been identified as M. Santu, 28, Amir Khura, 30, Trilochan Bhatra, 25, and Lalu Rana Kamara, 26. To remove the centring slab of a newly built septic tank measuring approximately 10 feet by 10 feet, two workers had stepped inside when the slab suddenly collapsed.

Another labourer entered the tank to rescue them, but all of them were trapped inside as more debris fell on them. A passerby, hearing their screams, steeped inside to rescue them. However, he also became a victim.

They fell unconscious due to a short supply of oxygen and the presence of toxic gases. Fire personnel rushed to the spot and pulled out all four persons. The three workers were pronounced dead on the spot, and the passerby who went inside the septic tank was admitted to the hospital and later passed away.