Israeli forensic scientists are examining bone fragments to see if they belong to the missing airman Ron Arad, Israeli sources say.
Israeli pilot Ron Arad has been missing since 1986
The sources said the remains had been handed over by a Lebanese group, but did not say if that was Hezbollah.
There have been reports that Hezbollah is about to swap Arad's remains for a Lebanese prisoner held in Israel.
The Israeli pilot was shot down over Lebanon 18 years ago, but his fate has never been confirmed.
Month of tests
Israel has said it believes he was held alive in Lebanon for some time after bailing out of his plane.
Israel Radio said it would be about a month before the results of the examination were known - but that defence officials were far from convinced the bones would turn out to be Arad's.
Israel has demanded proof of his fate before it will free Samir al-Qantar, a Lebanese gunman who killed four Israelis, including two children, in an attack in Galilee in 1979.
In a previous prisoner swap in January, 436 Arab prisoners and the
bodies of 59 Lebanese fighters were handed over in return for an Israeli businessman and the bodies of three
An Arab source close to the exchange talks told Reuters that "Arad is dead and Hezbollah has his remains".
The source said the group also had the remains of three Israeli soldiers who went missing on an operation in Lebanon in 1982.
The Israeli newspaper Haaretz quoted senior government sources who dismissed reports of an imminent swap involving Arad's remains as "media spin".