Russian plane crash: Bomb theory supported by ISIS chatter, officials say

ISIS' affiliate in Egypt says it brought down Metrojet Flight 9268. And U.S. officials are more confident that terrorists bombed the Russian plane.

Yet key questions remain: If terrorists did plant a bomb, how did they do it? And what could prevent that from happening again?

Here's the latest on what we know about the disaster that killed 224 people:

Several senior U.S. intelligence, military and national security officials have told CNN about the growing confidence that the plane was bombed by terrorists.

One official said it was "99.9% certain." Another said it was "likely."

The plane was headed from the Egyptian resort city of Sharm el-Sheikh to St. Petersburg, Russia, on October 31. But not long after takeoff, it disintegrated midair and crashed in the Sinai Peninsula.

Egyptian officials, who are leading the main crash investigation, haven't expressed as much confidence in the bomb theory.

"All the scenarios" are still on the table, said Ayman al-Muqaddam, the head of the investigation.

"We don't know what happened exactly," he said.

The Egyptians aren't the only ones involved. Experts from Russia, France, Germany and Ireland -- countries that are connected in various ways to the Airbus A321-200 that crashed -- are also investigating.

Source: cnn