Two brothers died of suspected asphyxiation on Monday in Cooch Behar when they got into an under-construction septic tank in an attempt to open its wooden shuttering.

Sources said around 9.30am, Nabi Haque, 45, of Boronachina-Kuthibari under Dinhata police station, got into the tank to open the shuttering. When he fell ill, his brother Sadikul, 43, entered the tank to rescue him. Both died inside.

“Owing to rainfall, water accumulated in the under-construction tank and it had to be cleaned. First, my father got into the tank. He fell sick breathing in noxious fumes and called for help. To rescue him, my uncle got in. However, he also complained of breathing problems. They didn’t come out,” said Manirul, Nabi’s son.

Residents informed fire services.

Jainal Abedin, their nephew, said the firemen brought out the brothers.

Both were rushed to the Dinhata subdivisional hospital where doctors pronounced them dead.