Passage: A gas explosion in a residential area of Rosario, the third-largest city in Argentina, occurred on August 6, 2013. It was caused by a large gas leak; a nearby building collapsed, and others were at high risk of structural failure. Twenty-two people died, and sixty were injured. Several organizations helped secure the area, search for survivors and aid people who lost their homes. Shortly after the explosion, the time needed for reconstruction was estimated at six months.

Question: Which hazard caused the collapse of a building in Rosario, Argentina, on August 6, 2013?
gas leak