On 24 March 1999, a transport truck caught fire while driving through the Mont Blanc Tunnel between France and Italy.

Other vehicles traveling through the tunnel quickly became trapped and they also caught fire as firefighters were unable to reach the transport truck.

On the morning of 24 March 1999, 39 people died when a Belgian transport truck carrying flour and margarine, which had entered the French-side portal, caught fire in the tunnel.

These fumes quickly filled the tunnel and restricted oxygen, disabling vehicles including fire engines which, once affected, had to be abandoned by the firefighters.

Many drivers near the blaze who attempted to leave their cars and seek refuge points were quickly overcome due to toxic components of the smoke, mainly hydrogen cyanide.

Without other possibilities, they abandoned their vehicles and took refuge in two of the emergency fire cubicles (fire-door sealed small rooms set into the walls every 600 metres (2,000 ft)).

When it was realized that the cubicles were offering little protection from the smoke, they began searching for the doors that led to the ventilation duct.

By 11:30, 37 minutes after start of the fire, smoke had reached the French entrance of the tunnel, 6 kilometres (3.7 mi) from the truck.

At 11:39, another team of firefighters entered the tunnel from the French side but were blocked at the garage 5, 4,800 metres (15,700 ft) from the truck.

[3] Authorities compounded the chimney effect by pumping in further fresh air from the Italian side, escalating the fire while trapping toxic fumes inside.

A remote site for cargo safety inspection was created on each side: Aosta in Italy and Passy-Le Fayet in France.

Pierlucio Tinazzi, an Italian security guard who died attempting to rescue a truck driver, was posthumously awarded Italy's Medaglia d'Oro al Valore Civile.

One account reported it to be a cigarette stub carelessly thrown at the truck, which supposedly entered the engine induction snorkel above the cabin, setting the paper air filter on fire.

Édouard Balladur, former president of the French company operating the tunnel (from 1968 to 1980), and later Prime Minister of France, underwent a witness examination.

Balladur claimed that the catastrophe could be attributed to the fact the tunnel had been divided into two sections operated by two companies (one in France, the other in Italy), which failed to coordinate the situation.