On the afternoon of June 4, 1989, two fully-loaded Russian passenger trains met a cloud of liquefied petroleum gas, resulting in a huge explosion. The blast rivalled that of the Hiroshima bomb, and killed over 500 people. Many were children, travelling to and from holidays on the Black Sea.
The LPG pipeline, carrying gas along some of the same route as the rail lines, was loaded with a mixture of propane, butane and other hydrocarbons, pressurized to keep it liquefied. Pipeline engineers noticed a drop in pressure in the pipe on the morning of June 4. Instead of searching for a leak they increased pressure in the line to maintain production. This resulted in two huge clouds of heavier-than-air propane gas leaving the pipe. The gas traveled a half-mile to the rail line and settled in a gully between the towns of Ufa and Asha.
Two trains were travelling between Adler, a Black Sea holiday destination, and Novosibirsk, a major Trans-Siberian Railway hub. One train was travelling in each direction; they were at full capacity with a total of 1200 passengers, many of them children. Both engineers noticed clouds of foul-smelling gas on the tracks. The passing of the two trains stirred the gas with air, making and extremely volatile mix. A spark from the track ignited the gas at 1:15 pm.
The fireball from the explosion expanded for 1.6 km, flattened trees for 4 km, and destroyed both trains. Over 500 people died; exact numbers are not known because many bodies were never recovered. 723 survivors were seriously injured, most from burns. The fireball was visible for 95 miles, and the explosion broke windows in Asha.
President Mikhail Gorbachev toured the disaster, and voiced his frustration at the lax safety procedures and lazy practices that led to the disaster, and that continued to hold Russia back from achieving its potential as a great nation.