Ufa train disaster

In 1989, a train disaster in Russia killed 575 people all because of a gas leak. Estimates of the size of the explosion have ranged from 250–300 tons of TNT equivalent to up to 10,000 tons of TNT equivalent. Without anyone knowing, a faulty gas pipeline 3,000 feet from the line had leaked natural gas liquids and weather conditions allowed the gas to accumulate across the lowlands, creating a flammable cloud.