Twenty-five people were taken to jail and another 15 were given house arrest on orders of Turin prosecutors who accuse the suspects of violence against public officials, inflicting bodily harm and resisting arrest.
Hundreds of police and demonstrators were injured on 27 June and 2 July when demonstrators threw Molotov cocktails at police during protests near Turin.
The ''No-TAV'' protest movement is opposed to the blasting of a tunnel in the Valle di Susa that will be part of a 15 billion-euro train line connecting Turin to Lyon. Thousands of people attend the demonstrations against the TAV, an acronym for "treno di alta velocita," or high-speed train.
Work on the main 58-kilometre tunnel, of which 12 km are in Italy, is due to begin in 2013 and go into service around 2023. The line will cut three hours off the current seven-hour train journey between Paris and Milan.
But the project has sparked fierce opposition including from residents, environmental groups and at least 23 local mayors. Protesters claim drilling to build the train link will damage the local ecosystem and could release potentially harmful substances.
Thursday's arrests were centred in the northern Piedmont region, though they were carried out throughout the country.