The Mont Blanc tunnel linking France and Italy re-opened to motorists today, almost three years after a horrific inferno that killed 39 people caused its closure.
The opening went ahead despite a small explosion earlier on the French entrance to the tunnel.
A maintenance truck was destroyed but there were no injuries, a local official said. The blast caused no damage to the tunnel itself, which has been closed since a 1999 truck fire killed 39 people.
No one immediately claimed responsibility for the blast, which occurred at about 3 a.m. (2 a.m. Irish time), said Mr Michel Bergue, an official of the Haute-Savoie region, where the French entrance to the tunnel is located.
The explosive device was described as low-grade, of the type used often in the Alpine area to trigger avalanches.
Two other attacks against the tunnel last year, while it was still closed to traffic, were claimed by activist groups that opposed truck traffic in the Alpine passage.
Demonstrations were planned today in protest at the tunnel's eventual reopening to trucks, which government officials say will happen next week.
Environmentalists and other critics say that trucks inside the 7.4-mile tunnel are too dangerous and cause excessive pollution.
In March 1999, 39 people were killed after a truck carrying flour and margarine caught fire and turned the passage into a deathtrap. The blaze burned for two days while firefighters tried to reach cars and people trapped inside.
AP