Construction works on the tunnel began in 1916 by Milan firm Giovini & Mora, but encountered significant delays due to the outbreak of war and the lack of manpower caused by the drafting of young labourers. It took one ton of gunpowder and half a ton of dynamite to dig the tunnel, and the excavated material was used to create the embankment between the stations of Lezza-Carpesino and Pontelambro, needed to overcome the 2.6% difference in level between the two stations. At the end of excavation the tunnel measured 346 metres and was the longest on the entire F.N.M. network.