Bhubaneshwar: Three labourers died of asphyxiation while carrying out roof-centering work on a septic tank in Odisha’s Sambalpur district on Saturday, while one is being treated at the hospital where his condition is stated to be critical, officials said.

Officials said the labourers were engaged in the centring work of a septic tank at an under-construction toilet in Pukuda village of Jamankria police station.

The toilet tank was constructed around four months ago, but the centring of the toilet tank was incomplete and was scheduled for Saturday, said officials.

The labourers after entering the septic tank, became unconscious due to suffocation, said officials, adding that others present at the spot immediately pulled them out and took them to the nearby hospital, where three were declared dead by the doctors.

The deceased have been identified as Srikant Munda, Bharat Rana, and Basant Dehury. Another labourer, Siddharth Mund, who became unconscious, has been shifted to the district headquarters hospital.

According to the doctors at the hospital, the cause of asphyxiation may have been due to the presence of toxic gases in the tank. These gases can include methane, hydrogen sulfide, ammonia, carbon dioxide, carbon monoxide, sulfur dioxide, and nitrogen dioxide.