To go on trial for raping someone under the age of 15 -- the age of consent in France -- there would need to be proof that the man attacked the girl, threatened or constrained her, or thrust himself upon her without her expecting it.
But investigators said they had insufficient proof that the sex was non-consensual.
Investigations resulted from police raids or reactive labor inspections from employee tips.
The government initiated prosecutions against 175 alleged traffickers, up from 38 initiated the previous year.
While authorities investigated these crimes, culpable officials typically avoided punishment.