Police have booked three officials of a chemical firm in connection with leakage of poisonous gas at the company's plant in Tarapur Industrial Estate in Maharashtra's Thane district, which resulted in the death of four workers.

Thane district police said they have booked chief manager, production manager and plant supervisor of Sequential Scientific Limited for culpable homicide not amounting to murder and negligent conduct with respect to poisonous substance as well as machinery.

Four workers were killed, while three others were admitted to a hospital in a critical state following the leakage of hydrogen sulphide gas at the plant belonging to the company at around 7.30 on Wednesday

The workers who were killed in the incident were identified as Naresh Varma, Dinesh Singh, Shivkant Tiwari and Prajapati, who was a supervisor at the plant. Three others, admitted to a local hospital, are now out of danger, police said.

Officials of the Maharashtra Pollution Control Board (MPCB) and the Department of Industrial Safety and Health (DISH) are also conducting independent enquiries into the incident.