Tragedy struck the factory, located in Palghar-Tarapur MIDC area, when the work of filling gas was on around 4 pm, said an official. Three workers of a chemical company near Palghar, nearly 115 km from Mumbai, died on Sunday following a toxic gas leak, the police said. In early March, three people were killed after nearly 40 explosions at a chemical factory in the area. The Tarapur MIDC area has several factories producing poisonous chemicals. The nature of the gas will be ascertained after port-mortem of the bodies are done, said another source..