WASHINGTON — (CNN) 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 a key question remains: If terrorists actually 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.

At least some of the intelligence intercepts being used to assess what happened to the jetliner came from Israeli intelligence, according to a U.S. official briefed on the intelligence as well as a diplomatic source.

The communications were captured by Israeli intelligence focused on the Sinai, and passed along to the United States and Britain, the sources said.

Israeli officials would not comment on the claims.

Muqaddam said Egypt had not been provided any information or evidence tied to reports suggesting that a bomb took down the flight, and urged the sources of the reports to pass along related evidence to Egyptian investigators.

The belief that a bomb was most likely to blame centers to a large extent on British and U.S. intercepts of communications after the crash from the Islamic militant group ISIS’ affiliate in Sinai to ISIS operatives in Syria, officials said.

The Sinai affiliate has publicly claimed responsibility for downing the plane, but so far hasn’t explained how it was done. That’s prompted questions about the claim among some observers, considering ISIS’ tendency to often publicize its acts for propaganda value.

The ISIS messages monitored by British and American intelligence agencies are separate from the group’s public claims, a U.S. official has said.

The two Western countries have been analyzing the specific language in the chatter to determine to what extent the operatives were talking about the type of bomb and detonator used, and whether that language was a true representation of what happened, one official told CNN.

Several officials said it’s the specificity of the chatter that has contributed to the U.S. and British view that a bomb was most likely used.

European investigators who analyzed the cockpit voice recorder and flight data recorder say the crash was not an accident, CNN affiliate France 2 reported.

The investigators said the cockpit voice recorder indicates an explosion, and the flight data recorder shows the blast was not accidental, the affiliate said.

But Muqaddam, the head of the investigation, did not echo those details.

He confirmed a noise was heard in the final second of the cockpit recording as the aircraft was on autopilot and ascending. But he offered no description of the sound, saying a specialized analysis would be carried out to identify it.

The crash might have been caused by a lithium battery or a mechanical issue, Muqaddam said.

He also said the investigation has been hampered by bad weather.

The remains of more than 100 victims have been identified through DNA testing, Russian Deputy Prime Minister Olga Golodets said, according to the state-run RIA Novosti news agency.

The vast majority of the passengers were Russian. The others were of Ukrainian, Belarusian or unconfirmed citizenship.

Russian media said the disaster created many orphans, as many parents left their children with relatives as they went on vacation to Sharm el-Sheikh.

The-CNN-Wire ™ & © 2015 Cable News Network, Inc., a Time Warner Company. All rights reserved. (PHOTO: Russian Emergency Situations Ministry)