Investigators are trying to determine the cause of an explosion that killed one person in a Los Angeles building believed used store nitrous oxide cylinders. Three people were injured in the Wednesday evening blast, the Los Angeles Times reported. Two of the victims were reported in fair condition Thursday. The building where the explosion occurred is located behind a store in South Los Angeles. The victims were all inside the building. A law enforcement source told the Times the building is used to store cylinders of nitrous oxide that power mini-bikes. Investigators believe someone was filling a cylinder when it blew up. The explosion is being investigated by the city\'s police and fire departments and the California Occupational Safety and Health Administration.