A poisonous gas leak at a pharmaceutical factory in the western Indian state of Maharashtra killed four workers and left 11 sick, according to the company and police. Preliminary investigations suggested that hydrogen sulphide gas escaped from a pipeline late Tuesday at the Sequent Scientific factory in Boisar, 120 kilometres (75 miles) north of Mumbai. \"There was an accident at our Tarapur facility. The effects were contained last night but resulted in the sad demise of four workers and injuries to a few others,\" the company said in a statement to the Bombay Stock Exchange. The factory has been closed since the accident. \"At least eleven workers who complained of nausea are still in hospital. They are out of danger,\" a Boisar police official told AFP. Three managers at the plant have been held for questioning, while the state government and the Department of Industrial Safety and Health have started investigating.