The 29-year-old Algerian Adel Haddadi and the 35-year-old Pakistani Mohamad Usman were charged with “criminal conspiracy with terrorists”, the source said of the men turned over earlier Friday by Austrian authorities.
Investigators believe they travelled to the Greek island of Leros on October 3 on the same boat full of refugees as two men who took part in the November 13 attacks.
Those two, thought to be Iraqis, blew themselves up outside the Stade de France stadium, one of a series of brazen assaults by around 10 people around the French capital.
But Haddadi and Usman were held up, detained by Greek authorities for 25 days because they had fake Syrian passports.
Once let go, they followed the main migrant trail and made it to Salzburg in western Austria at the end of November after the Paris attacks.
Austrian police commandos then arrested them in December at a migrant centre a few hours after French authorities informed them the men could be in the country.
Austrian police said on Friday “that during the entire journey and until their arrest the men remained in constant contact with the terror group ‘Islamic State’.”
After his arrest, Haddadi told investigators that he wanted to go to France to “carry out a mission,” according to a statement seen by AFP.
A source close to the investigation said that Haddadi “was meant to take part in the Paris killings with his travelling companions.”
After France filed a European arrest warrant, a court in Salzburg approved at the beginning of July the transfer of the two men to France.
Usman is reportedly thought to be a bomb maker for Pakistani extremist organisations including Lashkar-e-Taiba (LeT).
India holds LeT, allegedly linked to Al-Qaeda, responsible for attacks in 2008 in Mumbai that killed 166 people.
Usman unsuccessfully appealed against his transfer from Austria, saying he would not get a fair trial in France and that he feared for his safety.
Salzburg prosecutors added Friday that two more men, a Moroccan and an Algerian arrested eight days after the others, remained in custody.
In December prosecutors had said that the men, aged 25 and 40 at the time, were being held “because of indications of close contact” with the two now transferred to France.