Police have not made any arrests so far and are interrogating the four men.
Four men are being questioned in connection with the death of 32-year-old labourer while cleaning a sewer in northwest Delhi's Jahangirpuri, police said Monday.
Police are questioning the project manager and supervisor of a firm that had been given the contract for the maintenance of the sewer by the Delhi Jal Board, they said.
They are questioning two persons, who had accompanied the victim while he was cleaning the sewer, police added.
Police are probing whether the victim was forced to enter the sewer and whether he had any safety gear with him when he went inside.
They have not made any arrests so far and are interrogating the four men.
The man, identified as Dooman Ray, died Sunday after suffocating to death inside the sewer he had entered to clean along with two others.