ST. PETERSBURG, Russia (AP):

US satellite imagery detected heat around a Russian passenger jet just before it went down in Egypt's Sinai Peninsula, two US officials said yesterday. But the discovery doesn't resolve the mystery of why the plane crashed, killing all 224 aboard.

A missile striking the Metrojet Airbus A321-200 was ruled out because neither a launch nor an engine burn had been detected, one of the officials said.

The infrared activity that was detected could mean many things, including a bomb blast or that an engine on the plane exploded due to a malfunction.

Aviation analyst Paul Beaver said the heat picked up by the satellite "indicates that there was a catastrophic explosion or disintegration of the airplane," but doesn't reveal the cause.

"It doesn't tell us if it was a bomb ... or if somebody had a fight in the airplane with a gun. There is a whole raft of things that could happen in this regard," he said.

It also could indicate a fuel tank or engine exploding, although "engines are designed so that if something malfunctions or breaks off, it is contained within the engine," Beaver added.

Aviation experts

Both US officials spoke on condition of anonymity because they weren't authorised to discuss the information publicly. Some aviation experts had earlier suggested a bomb was the most likely cause of Saturday's crash, while some others pointed at a 2001 incident in which the jet damaged its tail during landing.

The Metrojet was flying from Egypt's Red Sea resort of Sharm el-Sheikh to St Petersburg when it crashed in the Sinai Peninsula after breaking up at high altitude, Russian aviation officials said.

Islamic State militants said they had "brought down" the Russian plane because of Moscow's recent military intervention in Syria against the extremist group. But the group did not provide any evidence to support its claim, and militants in northern Sinai have not shot down any commercial airliners or fighter jets.

Egyptian President Abdel-Fattah el-Sissi called that claim "propaganda" aimed at damaging the country's image, and he insisted the security situation in the Sinai Peninsula is under "full control".