BIJNOR: Three persons — two factory workers and their supervisor — died while cleaning an effluent treatment plant (ETP) at Barkatpur’s Uttam Sugar Mill in Bijnor Friday. Another worker was grievously injured while trying to save them.Supervisor Muneshwar Singh, 45, from Kabulpur, along with Kapil Dev, 40, from Tisotra, and Sopal Singh, 49, from Lalpur, were deployed to clean the ETP when they fell into a tank. Prabhat Kumar, jumped in to rescue them, but could not. After struggling, he came out and raised an alarm.Other workers brought the four men out of the tank and rushed them to a private hospital, where three were declared dead on arrival. The fourth one is recovering and is stable. Dr Birbal Singh said preliminary findings suggest the deaths were due to inhalation of poisonous gases produced as a result of chemical reaction inside the tank.Families of the victims arrived at the mill after getting the news and accused the factory management of compromising on safety measures and demanded action.Bijnor SP (city) Sanjeev Vajpayee said, “The bodies were sent for post-mortem, and an investigation is on.