An explosion at a Vietnamese firework factory has killed at least 21 people and injured 98 others, said a military rescue official. Most of the survivors sustained burns, AFP reported. The blast, which happened at a military owned-factory in the Thanh Ba district in Northern Vietnam, could be heard from several kilometers away, local media reported. The number of victims would have been greater had the blast not occurred on Saturday morning, when fewer than usual people were working. The factory is the only one in Vietnam that produces fireworks, which are mainly used for New Year’s holidays and other festivities.