Russian communications intercepted by U.S. intelligence agencies showed Russia believed the plane that crashed in Sinai, Egypt, on Oct. 31 was brought down by a bomb, U.S. sources familiar with the matter said on Monday.
The intercepts are among pieces of evidence leading U.S. officials to suspect that a device planted on Metrojet Flight 9268 exploded shortly after the Airbus A321 took off from the resort city of Sharm al-Sheikh, the sources said.
All 224 passengers and crew were killed when the plane crashed in the desert on the way to St. Petersburg, Russia.
Egypt and Russia have yet to formally announce the cause of the disaster.
Both countries dismissed as premature U.S. and British assessments last week that a bomb likely was responsible. Foreign airlines canceled a wave of flights to Egypt's Red Sea resorts following the crash.
After initially signaling normal air traffic would proceed, Russia late last week canceled holiday flights into Sharm al-Sheikh. Over the weekend, Russia mounted an airlift to repatriate thousands of Russian vacationers who had been stranded in Sinai after regular flights were canceled.