A top district police officer said Laltu Mondal (18) was killed while making chocolate bombs when flames engulfed the room from sparks in a wire.
Zilla parishad executive officer Tarun Roy said Mondal was preparing the fireworks with pujas round the corner when the fires caused a minor explosion killing him on the spot.
A police force cordoned off the area and search was on as locals claimed two or three more have died.