Agra, Dec 01 (ANI): Three out of four labourers who entered the well of a sewage treatment plant in Agra to clean it died due to leakage of Methane gas. The rescue team reached at the spot and rescued all the four from the well in which one is in a critical condition and three died. He has admitted to the SN hospital in Agra. The plant incharge was also one of those who died. The rescue operation went for 1 hour. Police have met the family members of victims and assured all possible help.