In Maharashtra, three officials of a chemical firm were booked by police in connection with leakage of poisonous gas at the firm's plant in the Tarapur Industrial Estate in Boisar near Mumbai last night. Four employees of the firm died due to the leakage. Police have booked chief manager, production manager and plant supervisor of Sequent Scientific Limited for culpable homicide not amounting to murder and negligent conduct with respect to poisonous substance as well as machinery.