The bus, which had been forced to travel through France after being blocked in Switzerland, was one of two that had been making its way to Brussels for a European refugee demonstration on June 26th.
French police kept the two buses for hours after they arrived in Chamonix from Turin, La Stampa reported.
“We found the police lined up as if they were the army,” Aboubakar Soumahoro, a spokesman for Italy’s European Caravan movement for migrants, was quoted as saying.
"We are all refugees. We have passports and residence permits, or at least the receipt for a renewal."
Five alleged illegal immigrants were then sent back to Italy after checks were carried out.
The immigrants arrived in France early on Sunday morning after first being blocked from entering Switzerland at the Great St Bernard Pass, where they were kept waiting for three hours.
They then decided to continue their journey through the Mont Blanc tunnel, which links Italy’s Aosta Valley with Chamonix, and were warned of what to expect in France by a toll gate operator, Soumahoro told La Stampa.
After several hours, the group was “acquitted” of any crime, apart from five, who were taken back to the Italian border.
“It’s worth remembering that these people aren’t tourists, but people who have had traumatic experiences.”
The buses resumed their journey to Brussels on Sunday afternoon.
France imposes strict border controls and in 2011 prevented all Italian trains carrying migrants from north Africa from crossing its borders.