At least seven people died and 10 others were injured in a blast at an illegal cracker unit being operated in a house in Jharkhand's East Singhbhum district on Sunday evening, police said.The incident took place at Kumardhubi village under Barsol police station in the district.Police sources said that a huge amount of explosive powder was stocked at the three-storey building, where the blast followed after it caught fire following a short circuit. The blast caused a larger fire which soon also engulfed other houses around.The injured have been admitted in local hospitals and some have been sent to neighbouring West Bengal. Senior police officials have rushed to the spot.