Investigators today will be scrutinizing surveillance tape and employee records at Egypt’s Sharm el Sheikh airport, from which the Russian jet took off, looking for a ramp worker who authorities say may have been recruited by ISIS to plant a bomb on the plane.

“ISIS may have concluded that the best way to defeat airport defenses is not to go through them but to go around them with the help of somebody on the inside,” Rep. Adam Schiff, D-Calif., who has received classified briefings on the investigation, said on ABC News’ “This Week” Sunday.

American authorities told ABC News that electronic intercepts of ISIS, both before and after the crash, indicated that ISIS was in communication with someone at the airport.