Kadipara, July 30: Fireworks stacked in a schoolroom during a display exploded as an electric bulb burst and charred to death seven persons in a Burdwan village late last night.

At least 18 others were seriously injured. Seven of them sustained 90 per cent burns, said a doctor at the Kalna subdivisional hospital.

Police said the villagers were making fireworks for display at the ongoing, three-day Jhapan festival in Kadipara, about 145km from Calcutta.

Those killed were identified as Rakhal Malik, 52, Prasanta Malik, 28, Khudu Dhak, 26, Sukumar Malik, 28, Asit Majhi, 20 and Gour Malik, 50.

“We celebrate the festival every year. Yesterday was the second day, when we traditionally have the fireworks display,” said Shyamal Dhara, who was watching the display in the village square.

Those making the tubri were inside the primary school building.

“The electric bulb burst, sparks fell on heaps of sulphur, charcoal and potassium nitrate and there was a huge explosion,” Shyamal said.

“When we reached the school, thick smoke was billowing out from the room where the tubris were being made,” said another villager, Moloy Ghosh.

Two of the three classroom doors were closed. “There were about 20 people inside. We broke the doors open and brought the injured out. All of them were burnt,” Ghosh added.

“We have ordered a probe to find out why the fireworks were being manufactured inside a school building without following the safety norms,” district magistrate Manish Jain said.

District primary school council chairman Saidul Haque said no permission had been sought.