Sixteen defendants face charges in the March 24, 1999, fire, which trapped cars, trucks and passengers in the Alpine passage linking France and Italy. The fire burned for more than two days and is thought to have started in a Volvo truck carrying flour and margarine. It consumed some 20 tractor-trailers and 11 cars.
Defendants include the Swedish truck maker Volvo AB, the truck's Belgian driver and French and Italian operators of the tunnel. Investigators have said they found defects in Volvo FH12 trucks, the type involved in the fire.
Twelve people face up to three years in prison if convicted of manslaughter, and four companies could face fines and other sanctions.
Judge Renaud Le Breton de Vannoise told the courtroom he would lead a ''search for truth, without concessions.''
Dozens of victims' relatives waited outside in subzero temperatures for seats in the courtroom.
''I want them to be aware of the evil they did,'' said Patricia Terejana, complaining that the companies had expressed no remorse.
Bonneville, which is on the highway to the tunnel, turned its village hall into a courtroom to hold up to 400 people for a trial that will be conducted in four languages and is expected to last three months.
Gilbert Degraves, the Belgian truck driver, has said oncoming vehicles flashing their headlights alerted him to a problem midway through the tunnel. After he stopped and checked beneath the truck, it exploded and became ''a ball of fire.''
Experts said an external heat source _ possibly a cigarette _ may have come in contact with the truck's air filter. French investigators said a two-way ventilation duct apparently left in the wrong position by Italian authorities may blown air into the tunnel instead of sucking smoke out.
An investigating judge said tunnel operators quickly turned on stoplights at the tunnel's entrance but waited about nine minutes before activating tunnel warning lights. Vehicles already inside unknowingly advanced toward the burning truck.
The tunnel's Italian operator has paid $17.6 million to some 220 relatives of the victims, a lawyer for the families said Friday.
The 7.4-mile passage was closed for more than three years while it was repaired and fitted with safety improvements.
