Two names on the AF 447’s passenger manifest also appear on a list of radical Muslims considered a threat to France, Sky News reported quoting French investigators. French secret servicemen established the connection while working through a list of those who boarded the Airbus in Rio de Janeiro, Brazil, on May 31, the channel said. Agents are trying to establish dates of birth for the two passengers and family connections the channel quoted a source as saying.

There is a possibility that the name similarities are simply a “macabre coincidence”, the source added, but the revelation is still being “taken very seriously”.

A source working for the French security services told Paris weekly L’Express that the link was “highly significant”.

The French police however appeared to downplay the possibility of a terror link and said this was a simple coincidence while ruling out a link to the accident.

A senior French officer was quoted as saying that the names were “simple namesakes” and dismissed the notion that the suspects were on board, adding that this line of enquiry had been dismissed.

The website of L’Express had also reported that French agents were making inquiries after finding the names of two suspected Islamist militants on the manifest.

While aviation experts have said it is certain that there were computer malfunctions, terrorism has not yet been ruled out.

A French submarine with advanced sonar equipment began searching on Wednesday for the flight recorders of the airliner, the French military said. The nuclear-powered submarine Emeraude was sent to the area to hunt the “black box” recorders, which may help explain the disaster and which are believed to lie on the ocean floor.