[Recovered debris of the EgyptAir jet that crashed in the Mediterranean Sea are seen in this still image taken from video]CAIRO (Reuters) - Egypt's air accidents chief said on Thursday that a vessel provided by French company Alseamar, which specialises in marine wreckage searches, will join within hours the hunt for the black boxes from crashed EgyptAir flight MS804. Ayman al-Moqadem said negotiations were also underway to contract a second firm to help in the search. The investigating team had also received radar imagery and audio recordings from Greece detailing the flight trajectory of the doomed plane and the last conversation between its pilot and Greek air traffic control, Moqadem said. ...