Washington, Nov 4 (EFE).– The chartered Russian passenger jet that crashed last weekend in Egypt’s Sinai Peninsula could have been downed by the Islamic State or a related jihadist group, according to the investigation into the tragedy being conducted by the U.S. government.

According to U.S. intelligence sources quoted by media outlets, investigators are examining the possibility that an explosive device could have been placed on board the aircraft by someone before it took off from Sharm el-Sheikh for St. Petersburg.

The sources mentioned by the media said, however, that no formal conclusion has yet been reached in the investigation.

On Wednesday, the Egyptian branch of the IS, Wilayat Sina, took responsibility for downing the plane, although it offered no details as to how that was done.

In an audio recording, the authenticity of which could not be confirmed, the terrorist group said that “soldiers of the caliphate announced their responsibility for the airplane incident.”

The MetroJet Airbus A-321 crashed on Saturday 23 minutes after taking off, killing all 224 people on board.

Multiple investigations into the crash are under way.

MetroJet executives have insisted the crash was due to an “external impact,” not a technical malfunction or pilot error, although Egypt has discounted the possibility of a terrorist act.

Meanwhile, U.S. National Intelligence Director James Clapper said two days ago that there is no “direct evidence” of terrorism in the crash and that it is “improbable” that Wilayat Sina has the ability to mount an operation of this kind.

The aircraft was at an altitude of about 10,000 meters (31,000 feet) when it disappeared from radar screens with no prior emergency call from the pilots.

Given that the tail section was found some 5 km (3 mi.) from the fuselage and other wreckage, which was scattered over a wide area of desert, it appears that the plane suddenly broke up in flight as could have happened when a bomb exploded, but experts doubt that the terrorist group has any missile weaponry that could have reached it at its altitude. EFE