A noise was heard in the last second of the cockpit voice recording from the Russian plane that crashed last week in Egypt's Sinai Peninsula, the head of the joint investigation team said Saturday, bolstering US and British suspicions that the plane was brought down by a bomb. However, investigation leader Ayman el-Muqadem warned it was too early to say what caused the plane to apparently break up in mid-flight. Analysis of the noise was underway. "All scenarios are being considered," he said during a news conference. "It could be lithium batteries in the luggage of one of the passengers, it could be an explosion in the fuel tank, it could be fatigue in the body of the aircraft, it could be the explosion of something."
US and British officials have cited intelligence reports as indicating that the Oct. 31 flight from the Sinai resort town of Sharm el-Sheikh to St. Petersburg was brought down by a bomb on board. All 224 people onboard, most of them Russian tourists, were killed. Islamic State extremists claimed they brought down the Metrojet flight, without offering proof, saying it was in retaliation for Moscow's airstrikes that began a month earlier against fighters in Syria. El-Muqadem said debris was found scattered across an 8-mile stretch of desert, indicating the Airbus A321-200 broke up mid-air, but initial observations don't shed light on what caused it. Some pieces of wreckage were still missing, while the recovered pieces will be taken to Cairo for analysis, he said. (Read more plane crash stories.)