The incident took place when the godown on the premises of Sarurpur police station in the district was being cleaned this morning, district police spokesperson said.
The fire broke out when crackers kept in the godown caught fire, the spokesman said.
The firecrackers were seized during raids at the time of Diwali, he said.
The injured have been identified as Sattar, Feru, Rajveer and Salim, the spokesperson said, adding that they had been admitted to hospital.