The factory was located in a congested residential area of Kalyani. "Our officers are inspecting the incident. The cause of the explosion is not known," a police officer was quoted as saying _*Read more:*_ https://www.telegraphindia.com/west-bengal/bengal-at-least-four-killed-in-explosion-at-firecracker-factory-in-nadias-kalyani/cid/2082195