The French state prosecutor reportedly has demanded all charges be dropped against truck maker Volvo over a fire in the Mont Blanc tunnel which killed 39 people in 1999.

A trial is under way into the blaze, which began when a Belgian-registered Volvo truck caught fire. Prosecutor Vincent Le Pannerer said there was no proof of a fault in the truck and said: "The court must be certain. If it is not, it must drop the charges against Volvo."

The court will now rule on his request, but is unlikely to pursue the case without his backing.