Seven workers died while cleaning an underground drainage tank at Venkateswara Hatcheries in Andhra Pradesh’s Chittoor district on Friday, IANS reported. Another worker has been admitted to a hospital, and is said to be in a critical condition.

Officials said the workers died because they inhaled poisonous gas. The district officials have ordered an inquiry into the incident. The hatchery told the police that the workers had entered the tank without informing the company’s supervisors, reported Deccan Chronicle.

One among the eight-member cleaning team was the first to enter the tank. When he did not come out, others went in one by one to save their fellow co-workers. When the villagers removed the ceiling of the tank and pulled them out, all seven were unconscious. While four of them died on the way to the hospital, three succumbed later.

The company has announced a compensation of Rs 15 lakh compensation each to the families of the deceased while the state government will pay them Rs 10 lakh each, according to IANS.

On February 13, two labourers who were cleaning a septic tank at a restaurant in Bengaluru died of asphyxiation. The Bengaluru Police booked the restaurant owner, manager and caretaker.