There is no debris to be found. The black box, which is supposed to be indestructible in a large explosion and should broadcast a homing signal for up to 30 days, has gone dark. Moreover, INTERPOL is looking into several passengers who boarded the plane using false passports, and whose tickets were reportedly purchased by an unknown Iranian benefactor.
Several theories have emerged as to what could have caused the flight to “vanish” out of thin air. None of them are, as of yet, conclusive.
We can probably rule out a mid-air explosion, because something like that would likely have left instruments operational for long enough that readings would have been transmitted back to flight controllers. Likewise, there would be a fairly wide debris field had such an explosion occurred at such a high altitude.