TNT equivalent
At 1:15 am, two passenger trains of the Kuybyshev Railway carrying approximately 1,300 vacationers to and from Novosibirsk and a resort in Adler on the Black Sea exploded, from the town of Asha, Chelyabinsk Oblast. Without anyone knowing, a faulty gas pipeline from the line had leaked natural gas liquids (mainly propane and butane), and weather conditions allowed the gas to accumulate across the lowlands, creating a flammable cloud along part of the Kuybyshev Railway. The explosion occurred after wheel sparks from the two passenger trains heading in opposite directions ignited this flammable cloud. Estimates of the size of the explosion have ranged from 250–300 tons TNT equivalent to up to 10 kilotons TNT equivalent. Many of the victims died later in hospital; official figures are 575 dead and over 800 injured, but an unofficial estimate of the number of deaths is approximately 780. 181 of the dead were children; many survivors received severe burns and brain injuries.