Three laborers who went to open the shuttering of the water tank died, this was the reason for the accident.

Three laborers who had gone to work in a water tank in Hans Enclave in Gurugram, Haryana have died. It is believed that all three died due to gas leakage in the tank. Post mortem of the dead bodies is being done.
Police station in-charge Inspector Arjun Dev says that all three died due to gas leakage in the tank built in the house under construction. Post mortem of the dead bodies is being done. After that the cause of death will be revealed.

this is the matter
It is being told that there was up to one feet of water inside the tank. All three became unconscious due to leakage of poisonous gas from it. He was taken to a nearby private hospital. Where he was declared dead.
All three workers were engaged in the construction work of the building for about 15 days. Sada police station has sent the bodies of all three for post-mortem. All three are being identified. The station in-charge said that the water tank is about eight feet in height.
Eight days ago, except for one and a half feet space, a linter was put in the rest of the space. This morning, first one worker came down to open the shuttering, when he did not come out for a long time, other workers also went down. Here all three workers were found unconscious.
All three were working in a house under construction under the contractor. Post mortem will be done after the arrival of his family. No complaint has been lodged in the police station yet. The contractor is absconding.