France said the plane had been banned from its airspace
A signal has been detected from the flight data recorders of the Yemenia airliner that crashed in the Indian Ocean on 30 June, officials say.
Comoran and French investigators say the signal was picked up during an underwater search.
They gave no indication when the flight recorders might be recovered.
The Airbus 310, going to the Comoros Islands from Yemen, came down in bad weather with 153 on board. A 12-year-old girl was the only survivor.
"Investigators from the BEA [France's accident investigation agency] have detected a signal from the flight recorders," Comoran lead investigator Ali Abdou Mohamed said in a statement that was received in Paris, the AFP reports.
The French agency later issued a statement, saying that "the BEA confirms that a signal from the two boxes was detected this morning during underwater searches to locate the flight recorders of Flight IY 626.
No official cause for the crash has yet been determined.
However, the European Union and France have both said they highlighted safety concerns over Yemenia planes and said the jet that crashed had not flown into EU airspace since 2007.
The French transport ministry said on Tuesday that the plane had been banned from France because of "irregularities".
But Yemenia responded by criticising "false information and speculation about technical problems" on the plane.
Many of the passengers were travelling to the Comoros but had begun their journey in Paris or Marseille on another jet operated by Yemenia, the national airline of Yemen, before boarding flight IY626 in Sanaa.
The only survivor - the 12-year-old girl - was found clinging to debris some two hours after the crash.
Doctors say the only survivor's condition has improved
Speaking later from a hospital in the Comoros Islands, Baya Bakari told her father how she had been thrown into the ocean and watched her aircraft sink.
She said: "Papa, we saw the plane going down in the water. I was in the dark, I couldn't see a thing.
"[And] on top of that, daddy, I can't swim well and I held on to something, but don't really know what."
The girl was later airlifted to a hospital in France.
HOW THE FLIGHT DATA RECORDER WORKS
Flight data recorders, or "black boxes", are in fact orange or red.
Commercial aircraft carry two. One logs performance and condition of aircraft in flight, another records conversations of crew and their contact with Air Traffic controllers during the flight.
The Crash Survivable Memory Unit (CSMU) contains a memory board surrounded by thermal insulation and steel armour that can withstand a crash impact thousands of times the force of gravity and survive in the sea at depths of 20,000ft (6,096m).
The CSMU is insulated to sustain temperatures up to 1,100C for up to an hour or "low" temperature fires of around 260C for 10 hours.
An underwater locator beacon fitted on recorders emits continuous ultrasonic "ping" when they come into contact with water. The signal can reach the surface from depths of 14,000ft.