No one was injured in the heist, said Marco Meletti, a spokesman for the Gruppo Battistolli armored transport company.
Meletti told the Italian news agency ANSA that gunmen blocked two armored delivery trucks on a high speed highway that leads toward Switzerland near the town of Saronno. Some news reports put the amount of booty at €10 million ($13 million) but Meletti denied that figure.
The gang set the rig on fire and used an explosive charge to break into one of the armored vehicles, Italian news reports quoted investigators as saying.
ANSA said the bandits, about 10 of them according to investigators, escaped by car after strewing nails on the road to slow down police. The escape cars were later found abandoned near a farmhouse.