Four persons including two brothers died probably due to Carbon Diaoxide present at the bottom of an unused well in North Kashmir’s Kupwra district on Thursday.Chief Medical Officer Kupwara, Dr Kounsar said that all these four persons were brought dead in Kupwara hospital. “I don’t know the actual cause of death. Things will become more clear after the post mortem, however, prima facie, drowning seems the cause of death,” she said.The incident occurred at Warsun area of the district and the deceased hail from Dard Hari Sanghdan. Locals told news agency KNT that a labourer after using a stair went deep into the unused well probably with cleaning purpose. The others who were waiting for him were anxious after he didn’t came out. One by one three persons including two bother went down and didn’t return. As the news spread that four persons have are not coming out from the well, police as well as locals started operation and dragged out all the four persons using ropes out form the deep well. All the four persons were unconscious when dragged out from the unused well in presence of police. They were taken to local Primary Health Centre where doctors referred them to Kupwara Hospital and there doctors declared them brought dead.They were identified as Muhammad Altaf Sheikh (35) son of Ghulam Mohiuddin, Muhammad Altaf Khan (26), Mumtaz Ahmed Khan (24) sons of Ghulam Mohiuddin, Showkat Ahmed Khan (26) son of Ghulam Hasan, all resident Sangdan, Dard Harie Kupwara. A police official said that it is yet not clear how these people died and they are waiting for the post mortem report. A medico while talking to KNT said that deaths that occur when workers enter unused wells or tanks to clean them are not due to poisonous gases, as is widely believed, but because of carbon dioxide which is present at the bottom. “Deaths in unused wells are common during summer. It is not poisonous gase, but carbon dioxide, whose presence depletes oxygen and eventually cause asphyxiation. Organic materials deposit at the bottom of unused wells. When they start decaying, they release carbon monoxide. It is converted into carbon dioxide after it reacts with oxygen. Since carbon dioxide has high density, it stays at the bottom and inner layers of the wells and tanks and replaces the oxygen present there. When a worker enters the well to clean it, he dies only because there is no oxygen at the bottom,” he explained. (KNT)