At least four people including two children were killed when a gas cylinder exploded here the other night. The gas cylinder blew up in a house located in Zafarwal tehsil of Narowal, killing a man, his wife and two daughters. According to rescue sources, a fire broke out following the explosion that took place due to leakage in a gas cylinder at a three-story house in Zafarwal Chowk, resultantly four people of a family killed.