New Delhi: Days after poisonous gas at a sewage treatment plant killed two labourers, two cleaners died inside a Rohini sewer on Wednesday morning. Shankar (40) and Manoj (19), reportedly inhaled poisonous gas while cleaning a sewer in Sector 3, Rohini. Police said the sewer is in Delhi Development Authority’s (DDA) charge. “A case of causing death due to negligence has been registered against a private contractor identified as Arun,” said a Delhi Police official. DDA officials said the private contractor had asked the labourers to clean the sewer. “A hotel is being built in the vicinity, and because of that, unauthorized construction was done up to the manhole. It led to sewer blockage. To resolve the problem, the owners hired labourers,” said DDA spokesperson Neemo Dhar. The victims lived in the heart of a slum, near M2K mall in Rohini. On Thursday afternoon, the neighbourhood had gathered around Manoj’s mother to console her. Barely able to speak about what transpired on Wednesday morning, when her son had gone out with Shankar to clean the sewer, she called for Rahul, Manoj’s friend, who had been present at the site. “The contractor came to them in the morning and asked them to clean the sewer located near the mall. Manoj had never done such work before and refused to enter, but he was compelled to do the job,” alleged Rahul, adding the contractor promised both Rs 1,000 each for doing the job and Manoj, who was unemployed, accepted the offer. “I went along with him and Shankar. While they were doing their work, I sat a few metres away and talked on the phone. When I turned to check on Manoj, I could not spot anyone,” said the 21-year-old. Rahul said Shankar entered the sewer first. “When he collapsed inside, Manoj went in to save him. But even he collapsed,” said Rahul. Rahul claimed he pulled out Manoj and the police brought out Shankar. Shankar, originally from Bihar, had been living with Manoj’s family for the last couple of years. Ramkali, Manoj’s mother, said while Shankar often worked as a day labourer, her son had gone to clean a sewer for the first time.