The investigation into the cause of a Saturday airliner crash in Egypt's Sinai Peninsula is now focusing on who was onboard the plane and who had access to it before takeoff,
NBC News reports.
Egyptian security at Sharm el-Sheikh Airport is looking at who had entry to the departure hall, who was on the cleaning and catering crew and who was in the departure lounge, NBC quoted an airport source.
All 224 people aboard the Metrojet Airbus A321 were killed in the crash as it left with a flight mostly filled with vacationers returning to St. Petersburg.
American intelligence said satellites show no heat trail heading toward the airliner, meaning it would not have been hit by a missile. Islamic State (ISIS) militants have claimed credit for the attack, implying they placed a bomb onboard.
U.S. officials have said that is a possibility, but none of the passengers or crew on board are in American terror databases, NBC reported.
The other theory is mechanical failure, which most have deem unlikely even though a previous repair was made to the plane's tail section in 2001 after it hit the tarmac on landing.