The latest U.S. intelligence suggests that the crash of a Russian passenger jet flying over the Sinai Peninsula in Egypt was most likely caused by a bomb on the plane planted by ISIS or an ISIS affiliate, according to a US official familiar with the matter.
"There is a definite feeling it was an explosive device planted in luggage or somewhere on the plane," an official, familiar with the latest U.S. intelligence analysis of the crash, said.
"While the investigation is still ongoing we cannot say categorically why the Russian jet crashed," Prime Minister David Cameron's office said in a statement. "But as more information has come to light we have become concerned that the plane may well have been brought down by an explosive device."
An Egyptian source close to the investigation said that the cause of the crash is looking more like an explosion.
"It is believed to be an explosion but what kind is not clear. There is an examination of the sand at the crash site to try and determine if it was a bomb.
"There are forensic investigations underway at the crash site. That will help determine the cause, to see if traces of explosives are found," the Egyptian sourse said.
A Russian aviation expert said that investigators are looking into the possibility that an object placed on board caused the disaster.
"There are two versions now under consideration: something stowed inside (the plane) and a technical fault. But the airplane could not just break apart in the air - there should be some action. A rocket is unlikely as there are no signs of that," the Russian source said.