It was a Wednesday morning around 10:45 a.m. when 57-year-old Belgian Gilbert Degraves passed the toll booth on the French side of the Mont Blanc Tunnel with his 40-ton truck. The truck is loaded with margarine and flour destined for a food factory in Milan.

The 11.6 kilometer long Mont Blanc Tunnel is the deepest tunnel in the world and is located 2,478 meters below the summit of Europe’s highest mountain at 4,810 meters. When the first cars rolled through here on July 19, 1965 after four years of construction, the French and Italians had completed a project of the century. Only this tunnel made year-round road traffic across the Alps between Chamonix on the French side and Aosta on the Italian side possible. The tunnel has 18 fire shelters – one every 600 meters – and 77 emergency telephones.

After about two kilometers in the tunnel, white smoke rises behind the cab of Degrave’s truck, but he only notices it when he is already in the middle of the tunnel. The professional driver turns on the hazard lights. At around 10:52 a.m. the smoke was so thick that it triggered the tunnel sensors, which react to poor visibility in the tunnel. The driver finally stops the truck and gets out. A traffic jam quickly forms. Then suddenly the driver’s cab is on fire and is ablaze. The driver escapes from the tunnel shaft towards the Italian side.

At 10:54 a.m. a call from an emergency telephone reached the Italian control room. The sensors had only triggered the alarm on the French side; on the Italian side it was switched off the day before due to a false alarm. Finally the tunnel is closed to further vehicles and the rescue workers are on their way.

As the smoke becomes more and more intense, the first cars that had driven into the tunnel from Italy turn around again. An employee in the control room, who is observing the scenario via cameras, pumps fresh air towards them. A fatal mistake: the murderous smoke shoots over the cars behind the burning truck at 4.5 meters per second. Soon the entire French side of the tunnel is filled with smoke.

The smoke blackens the surveillance system’s video cameras. The rescue workers do not know that many people are trapped in their cars behind the burning truck. In a panic, some of them try to drive away. But because of the lack of oxygen, the engines fail. A few leave their vehicles to go to the fire shelters. However, most people lose consciousness after a few minutes due to the thick, toxic smoke.

When the Italian rescuers got within a few meters of the truck, there was suddenly a bang. “There were six explosions, very close together,” recalls an eyewitness in a TV documentary about the accident. “It just went bang, bang, bang, bang, bang, bang. Really fast. Those were really powerful explosions.”

It’s the tires that explode and shoot through the air like bullets. The firefighters retreat, rescuing a few people from the vehicles along the way. The fire has now spread to other cars. Next to the Belgian’s Volvo, another truck was loading margarine. Margarine has a very high energy content. When melted it is almost as dangerous as gasoline. And two more of the 14 trucks trapped in the tunnel were also carrying large amounts of polyethylene. They make the inferno rage even worse. Even experienced experts are surprised that a truck loaded with margarine and flour can burn as badly as a tanker loaded with 30,000 liters of gasoline.

The temperature in the tunnel is now more than a thousand degrees. A cruel heat that even the shelters cannot cope with. Above the source of the fire, the steel reinforcement of the concrete ceiling melted over a length of around 100 meters, and pieces of stone weighing tons crashed onto the vehicles. At some point the firefighters will no longer be able to get to the source of the fire.

The fire rages for three days. Little remains of the victims other than tooth remains, ashes and wedding rings. The last victim cannot be identified until five months after the disaster. Fire protection technicians suspect the cause to be a discarded cigarette butt, which may have ignited the air filter of the Volvo FH12.

In a subsequent trial, a total of 16 defendants will have to answer for negligent homicide. The then president of the French tunnel company ATMB, Rémy Chardon, received a two-year suspended prison sentence and the tunnel companies were sentenced to fines totaling 300,000 euros.

The driver of the truck also received a suspended sentence of four months. He tells the judges he did everything he could do. Even in the trial six years after the disaster, he doesn’t know what he could do better in a similar situation. “I couldn’t do anything else,” said Degrave, who said in a 2002 interview with Stern that he felt the justice system was trying to make him a scapegoat. His boss at the time fled to Ecuador because of the matter. “It turned out that he was letting me work illegally. As a result, trade unions and associations withdrew from me. I am not entitled to any support.” He denied responsibility for the disaster.

Looking back, experts say quick and decisive action would have saved dozens of lives. Nine precious minutes passed before the traffic lights at the ends of the tunnel turned red. If this had happened earlier, at least eight and possibly up to 22 people could have been saved.

The accident completely shut down the Mont Blanc Tunnel for around three years and sparked a worldwide discussion about safety precautions. Today it is praised for its modern safety and ventilation systems. The fire protection rooms were redesigned and now offer direct access to the escape tunnel under the road. With the new ventilation system, the air can be directed in a targeted manner and in the event of a fire, the toxic smoke gases are automatically blown out of the tunnel. Today, the only thing that reminds us of the catastrophe back then is a memorial with a stone memorial near the tunnel entrance.

Watch the video above: It is one of the most ambitious infrastructure projects in the world: The Fehmarnbelt Tunnel is being built less than two hours’ drive from Hamburg. It could create new relations between Central Europe and Scandinavia. However, critics point to ecological damage.

Sources: National Geographic,,