The vehicle was searched in an anti-drug operation as it crossed into Italy at the Mt. Blanc Tunnel earlier that day, the national police said on social media.
"The explosives have been seized and an investigation is underway," law enforcers said in a Facebook post that carried a photo of a batch of trinitrotoluene (TNT).
A 56-year-old man from Bosnia was reportedly behind the wheel. The explosives were discovered under the control panel of the vehicle, which is believed to have been on its way to the Balkans.