A U.S. infrared satellite detected a heat flash over Egypt's Sinai Peninsula at the time when a Russian plane crashed on Saturday, killing all 224 people on board, CBS News reported Tuesday.
Satellite data was still being analyzed, and it is unclear whether the flash was due to a bomb or an explosion in the aircraft's fuel tank or engine due to mechanical failure, the report said.
The cause of Saturday's plane crash, the deadliest in Russian history, is still a mystery. Investigators are examining wreckage in the Sinai and the plane's black boxes after the aircraft crashed from high altitude less than 30 minutes after takeoff.
Russian officials had immediately after the disaster dismissed claims by the Islamic State terrorist organization that it had downed the plane in revenge for Russian air strikes against rebels in Syria, but investigators have not ruled out that a terrorist attack was to blame.
The RIA Novosti news agency on Tuesday cited an unidentified Egyptian source as saying no trace of explosives had yet been discovered on the wreckage.
Other sources told the TASS news agency that material that did not belong to the downed plane had been found at the crash site.
The company that flew the jet, Kogalymavia, on Monday ruled out pilot error or mechanical failure as causes of the crash and blamed a “mechanical impact on the aircraft.” But Russian officials quickly cautioned that the conclusions were premature.
Three Kogalymavia aircraft have been involved in accidents since 2010, two of which were fatal.