At least 12 people were killed Tuesday when a gas leak set off an explosion that brought down part of an apartment building in Argentina. The blast in Rosario, the country\'s third-largest city, left at least 60 people injured and 15 missing, The New York Times reported. Rosario Mayor Monica Fein said the leak was on the ground floor of the nine-story building. The explosion early in the morning brought down the central block and damaged adjoining sections of the building, which were also at risk of collapse, officials said. Franco Jariton told the Times he was asleep on the seventh floor. \"I woke up and there were no walls,\" he said. Litoral Gas denied receiving any calls about a leak, although area residents said they had called to complain about a strong gas odor.