Two workers died and as many fell ill after allegedly inhaling some poisonous gas while cleaning a septic tank at a residential apartment complex in Gachibowli area here on Sunday, police said.
The bodies of the labourers aged 32 and 40, were pulled out from the tank.
The workers were employed to clean debris accumulated inside the tank. Initially, two of them entered it but came out immediately and then two others got in but were asphyxiated, they said.
The duo entered the tank without any safety gear, they added.
The condition of two people who were hospitalised is said to be stable.
A protest was held by some relatives and others demanding action. A case was registered.