The victims were identified as Anupam Sahu (40) and Bharat sahu (22), a labourer from nearby Khutmanbehera village, police said.
The labourer had entered the newly constructed septic tank through the manhole yesterday to remove the cover but when he did not come out houseowner Anumap also went inside, he said.
When both of them failed to come out, the fire brigade was informed and their bodies were recovered.