
The blast in Bhadohi district in Uttar Pradesh state caused widespread damage and local residents arrived to find only dead bodies in the debris of the shattered building.
A senior state police official told journalists the factory was being run under the guise of a carpet manufacturing business.
“Special teams including bomb and forensic experts are reaching the site to help and investigate,” the officer added.
Media reports said a huge quantity of illegal explosives was stored at the factory.
Explosions often occur in illegal firecracker workshops, especially around the Hindu autumn festival of Diwali. In October, a blast at another firework factory in Uttar Pradesh killed seven people.