ATHENS (Reuters) - Greece said it had deployed air assets and a frigate to an area in the southern Mediterranean where an EgyptAir aircraft vanished from radar screens early on Thursday. A defence ministry source said authorities were also investigating an account from the captain of a merchant ship who reported a "flame in the sky" some 130 nautical miles south of the island of Karpathos. (Reporting by Michele Kambas; Writing by Lincoln Feast; Editing by Paul Tait)