Three members of a family, including a toddler, were killed on Tuesday in an LPG cylinder explosion at their house in West Bengal's Howrah district, police said.The incident took place in Kulgachia area under Uluberia police station."A cooking gas cylinder exploded causing a big blaze. Three people including a three-year-old child have been killed in the incident," said a police officer.The victims have been identified as Mousumi Ghosh, her three-year-child Ayan, and the child's grandmother Gayatri Ghosh.