New Delhi: A sanitation worker and a security guard who had jumped in to save him suffocated to death inside a sewage treatment plant at a residential society in Noida on July 26, Indian Express has reported.The incident occurred at the Eldeco Society in Sector 150. The report says that the sanitation worker was 40-year-old Shashikant Sharma who is originally from Karauli district in Rajasthan, and the security guard is 22-year-old Akash, from Firozabad in Uttar Pradesh.Four people have been taken in by police for questioning, police told the newspaper.Deputy Commissioner of Police of Greater Noida, Ravi Shankar Nim, said that police have registered a first information report on the basis of the complaint of the families of the victims.Police personnel and the fire brigade team reached the spot and took them to Kailash Hospital, Nim said.Police said Sharma had lost consciousness inside the tank, which was located on the ground floor of the society and Akash had gone inside it in an attempt to rescue him.Akash worked extra hours at night, his colleagues told Indian Express.Chief Fire Officer Pradeep Kumar Choubey told Millennium Post that rescuers equipped with breathing apparatus entered the nearly 40×40-ft sewage treatment plant, which contained no water but was filled with poisonous gases, including methane and carbon dioxide.