A gas explosion at the Indiana State Fairgrounds Coliseum in Indianapolis on October 31, 1963, killed up to 81 people and injured about 400 others. It was one of the worst disasters in the history of both the city and the U.S. state of Indiana.
On that night, over 4,000 people were in the arena to watch a Holiday on Ice performance. While this was happening, liquefied petroleum gas was leaking from a tank that was stored with several others in a supply room underneath a part of the grandstands. Shortly after 11 p.m. ET, the gas came into contact with an electrical heating element from the concessions area, causing a major explosion that killed many seated above the room and caused significant damage to the stands. After the initial blast, while people were evacuating, a second blast caused by the remaining, unexploded tanks caused further destruction. Firefighters and other emergency responders were at the site within minutes and survivors were transported via ambulance to various hospitals in the area. The gas tanks were discovered by firefighters during cleanup operations and later testing revealed that they were the cause of the explosion.