Seventy years ago to this day, one of the worst ever artificial explosions unrelated to the use of atomic weapons took place in Switzerland. In the Blausee-Mitholz area in the Bernese Alps, 1947, shortly before midnight, an explosion cut through the pre-Christmas silence. Some 7,000 tonnes (15 million pounds) of ammunition exploded, along with the underground warehouse in which it had been stored. 

The detonation injured several people and killed nine, among them four children. Many houses in the Mitholz area were completely destroyed.

The series of explosions which shook the valley were so strong that they were registered by the seismological service in Zurich - 115 kilometres away. 

Jets of flames, hundreds of metres high, shot up into the night sky. The ammunition and debris that were expelled destroyed up to 100 buildings in the valley. The rock face, in which the ammunition storage room had been located collapsed and 250,000 cubic metres of rock were released. Huge boulders, weighing several tons were thrown across a distance of several hundred metres. Rubble, splinters and the burning remains of ammunition were scattered along a large radius surrounding the explosion. 

The catastrophe was one of the worst-ever artificial explosions which had ever been caused without the use of atomic weapons. To this day, the cause of the accident remains a mystery. 

Translated and adapted from the German by Laura Németh, swissinfo.ch 

(Images Walter Studer/Photopress-Archiv/Keystone)

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