Four persons, three of them engineers, died after inhaling poisonous gas in a sewage treatment tank at Hyundai's second car plant at Irungattukottai near Sriperumpudur, 50 km from here on Friday night, police said.
 The victims were employees of Pune-based Thermax Corporation which had undertaken to erect and commission the effluent treatment plant.

  The accident occurred when an engineer entered the tank, where paint and other chemicals were stored, to repair a malfunctioning motor and inhaled hydrogen sulphide and methane gas, Hyundai Motor India's vice-president (HR) S Ganapathi told Deccan Herald.

  He said three others, including a contract worker, died when they entered the tank to rescue the engineer. A fifth one, who also went to their rescue, managed to escape and had been admitted to hospital.
 Hyundai Motor India and Thermax Corporation have announced an ex-gratia of Rs 2 lakh each to the next of kin of the deceased and Rs 1 lakh to the worker in hospital.