According to them, the explosion took place yesterday after gas leaked from an LPG cylinder at the house.
"Four persons, including the 60-year-old owner of the house, Wakil Miyan, sustained grievous burn injuries," SP Rakesh Shankar said, adding firecrackers were being manufactured in the house.
They were admitted to BRD Medical College, Gorakhpur, the police said.
"Wakil Miayn died today during the course of treatment, while Gulesra, Mannu and Arman are undergoing treatment," the SP said.