Subsequently, the house owner and another labourer also went inside but they too did not come out following which the locals informed the police, he said.
The four were later pulled out of the septic tank and taken to a local hospital where they were declared dead, the police official said.
Prime facie, it is suspected that they died of suffocation inside the newly-built septic tank, he said.
A case was registered in connection with the incident, he said.
The deceased were identified as the house owner, Satyanarayan Kushwaha (64), his son Bhanu (32), and two workers Vijay Kanwar (30) and Jhemal Kanwar (40), he added.
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