British and American intelligence officials intercepted "chatter" among Islamic State (Isis) militants in Syria's Raqqa region and their affiliated Islamists in Sinai shortly after the Russian passenger jet with 224 people crashed. The intercept has strengthened the speculation that a bomb inside the plane could have brought it down.
American intelligence sources told NBC News that IS operatives were heard bragging about taking down the aircraft shortly after the Airbus A321, operated by Russia's Metrojet airlines, crashed in Sinai. An official said IS jihadists in Sinai and their counterparts in Raqqa were "clearly celebrating".
Another intercept just before the crash indicated that a major attack was imminent but did not mention any plane. None of the sources who spoke to more than one media outlet were ready to be identified due to the sensitive nature of the incident.
"The theory of an explosive device, with local complicity, is being taken seriously. Nothing is proven yet, but it is a real possibility. They believe that what Daesh (Islamic State) is saying has a good chance of being credible," a European official, who was briefed by an intelligence agency, told Reuters.
As soon as the plane went down killing all the people on board, a Sinai-based Islamist militant group, which pledged allegiance to IS, claimed responsibility for the attack. The claims were immediately shot down by authorities saying the extremists do not possess the capability to bring down an aircraft cruising at 30,000ft.
Russia, which was initially sceptical of the UK's move to stop flights to Egypt, has also swiftly followed suit suspending all flights to and from Egypt. Russian authorities, however, maintain there is no credible evidence to suggest it was a terror attack.
Subsequent to US President Barack Obama's statement that it was possible that a bomb brought down the plane, White House spokesperson Josh Earnest said: "There is information that is known by the — by the US government — that led the president to make that statement." Egypt, which is overseeing the investigation along with Russia, has refused to comment on the speculation until the probe is completed.