In contravention of the Geneva Convention, the shelter occupied by civilians contained boxes of ammunition, next to the gasoline cans powering the German generator. At 2:30 a.m. on Friday night, September 9, violent explosions were heard on the Tourville side. The shape of the site made it a cannon, and the tunnel burst into flames. Survivors' accounts differ as to the cause of this catastrophe: an altercation between German officers, an improperly extinguished cigarette, a false move to switch on the generator. As proof of this, the flames escaping from the two entrances to the shelter: the tunnel had been transformed into a veritable furnace, asphyxiating and burning everything.
The catastrophe occurred on the night of September 8-9, 19442. At 2:30 a.m., a Todt soldier in charge of the generator powering the shelter got up to start it. Following a false maneuver, a fire broke out. Nearby was an emergency generator used for lighting, and next to it a fairly large reserve of fuel. Finally, a large quantity of ammunition was stored in the shelter.
Those who reacted quickly emerged into the smoke after climbing the 154 steps of the staircase. A dull roar of enormous power shook the vault. Those at the end of the tunnel are thrown out like chaff. The others are either pinned against the grate, which has closed under the impact, or dead inside.
All the ammunition exploded, turning the long tunnel into a veritable cannon. The flames rose 30 meters above the entrance. 371 Frenchmen died, burnt to a crisp in a single blast; five to six hundred Germans were killed. Victor Eusen was among the victimsSource Wikipedia