Greek state television now reporting that Greek planes taking part in the SAR have spotted debris in the form of "large orange chunks" that are thought to belong to the missing plane. Similar reports are coming from the Greek SAR Coordination Center and the Hellenic Coastguard. The MOD has not yet confirmed the report.
Edited to include Hellenic CAA statement, which just confirms times and actions (all times local, Greek local time is UTC+3):
0224: entry into Athinai FIR
0248: handoff to next Athinai sector and clearance for exit point. The pilot was cheerful and thanked ATC in Greek.
0327: ACC tries to contact the plane for handoff information to Cairo ACC. Plane non-responsive, call is repeated on emergency freq.
0329: Plane crosses the FIR exit point
032940: Plane trace lost, approx 7nm SSE of KUMBI, within Cairo FIR. Military radar raised, negative return.
0345: SAR activated, Cairo notified.