Passports belonging to Bordeaux's Fernando Cavenaghi (pictured) and Diego Placente, Toulouse's Mauro Cetto and Olympique Marseille's Renato Civelli, who all have dual Italian nationality, were being looked at, said the source, who declined to be named.
"The French League has contacted the Italian consulate in Paris and asked them to bring the matter to the Italian authorities," the source explained.
"There are suspicions of false passports in Ligue 1. For us, the passports are valid, they were validated by the league but anticipating possible protests at the end of the season, we contacted the Italian authorities."
Toulouse said that Cetto's Italian nationality was fully justified.
"His grandparents, on his mother's and father's side, are Italian and the player, according to Italian laws, benefits from the Italian nationality," Toulouse said in a statement on their website.
