'Still no conclusions' on why Russian plane broke up

Investigators have still not determined why a Russian airliner broke up over Egypt's Sinai killing 224 people, the probe's chief said Saturday, amid growing suspicions the cause was a bomb.

"Initial observations... do not allow for identifying the origin of the in-flight break-up" of the Airbus A-321 last Saturday 23 minutes and 14 seconds after it took off from the Red Sea resort of Sharm el-Sheikh, Ayman el-Mokkadem said.

"A noise was heard in the last second of the recording by the cockpit voice recorder" and "a spectral analysis will be done to determine the origin of this noise", he told a press conference.