pax, you are right, in French we do not have the distinction can/may.
Thus the sentence is quite affirmative.
wiggy, translating La Dépèche : "The signal is definetely coming from one of the recorders..."
in the next sentence the BEA boss says the signal has been detected (like pax has emphazised), recalling that Egypt had, before that, announced it was probable.
Thats is a logical chronology : first probable (source Aegypt), then certain (source BEA)
BTW French people often make mistakes just because they use "can" for "may" or conversely !