Six-year-old Parth, who was rushed to hospital after being rescued with other children, was declared brought dead, they said.
"The children were bursting crackers on the rooftop of Govind Nagar colony at around 6 PM when the top of an old septic tank caved in due to one of the explosions," a police official said.
"On the hue and cry of children, people rushed to the spot and police and fire brigade were informed. While five children were saved, the sixth was rushed to District Hospital," said city Magistrate Ram Araj Yadav.