Two passengers with names linked to Islamic terrorism were on the Air France flight which crashed with the loss of 228 lives, it has emerged.
French secret servicemen established the connection while working through the list of those who boarded the doomed Airbus in Rio de Janeiro, Brazil, on May 31.
Flight AF 447 crashed in the mid-Atlantic en route to Paris during a violent storm.
While it is certain there were computer malfunctions, terrorism has not been ruled out.
Soon after news of the fatal crash broke, agents working for the DGSE (Direction Générale de la Sécurité Extérieure), the French equivalent of MI6, were dispatched to Brazil.
It was there that they established that two names on the passenger list are also on highly-classified documents listing the names of radical Muslims considered a threat to the French Republic.
A source working for the French security services told Paris weekly L'Express that the link was "highly significant".
Agents are now trying to establish dates of birth for the two dead passengers, and family connections.
There is a possibility the name similarities are simply a "macabre coincidence", the source added, but the revelation is still being "taken very seriously".
France has received numerous threats from Islamic terrorist groups in recent months, especially since French troops were sent to fight in Afghanistan.
Security chiefs have been particularly worried about airborne suicide attacks similar to the ones on the US on September 11, 2001.