Last Updated Nov 2, 2015 11:34 AM EST
CAIRO -- The Russian owners of the Airbus jetliner that broke up in the air before crashing Saturday in Egypt, killing all 224 people aboard, claimed Monday morning that the crew reported no problems during the flight, and the cause of the tragedy "could only have been a mechanical impact on the plane."
But the Reuters news agency quoted an Egyptian official on the committee investigating the crash as saying a preliminary examination of the plane's flight recorders, or "black boxes," suggested no external object hit the aircraft.
In addition, the U.S. intelligence community has determined with a high confidence that there was no external event -- in other words, no missile or other object impacting from outside the aircraft -- that caused the structural failure of the plane. Sources in the intel community told CBS News the conclusion was drawn based on imagery of the plane and the crash site.
James Clapper, the U.S. director of national intelligence, confirmed that view to the Associated Press, saying it was not impossible for extremists to have carried out the attack.
"It's unlikely, but I wouldn't rule it out," he said.
The boxes themselves -- the cockpit voice recorder and the flight data recorder -- were in good condition, according to Russia's emergency situations minister.
Reuters quoted the unnamed official as saying -- as did the senior executive of Metrojet at the Monday morning news conference in Russia --that no distress call was made by the flight crew before the plane lost contact.
CBS News correspondent Allen Pizzey says the recovery of the bodies from the crash site was expected to be completed by the end of Monday, according to Russian officials. The first remains were repatriated to the Russian city of St. Petersburg, from where the victims' holiday trip began.
Family members were to provide DNA samples and other means of identification at a crisis center set up close to what has become an impromptu memorial for the victims -- at least two dozen of whom were children.
Finding all the bodies, and evidence of what happened, would be a painstaking task, says Pizzey; the debris is scattered over an area covering almost eight square miles. A child's body was found some five miles from the site of the main wreckage.
The size of the debris field indicates a catastrophic event, according to aviation experts.
"All signs prove that the structure of the plane disintegrated in the air at a high altitude," Russian transport agency head Alexander Neradko said.
Claims from an ISIS-affiliated group in the Sinai Peninsula, the volatile Egyptian region where the plane went down, that it had a hand in the crash have been widely dismissed by Egyptian and other officials and experts.
"They have a track record of making claims that aren't right, so it's really hard to say, just on the basis of their claim, what happened here," noted CBS News senior security contributor Mike Morell, the former deputy chief of the CIA.
The final word on what caused the crash will, hopefully be contained in the black box recorders, which will be examined by experts from France, Russia, Egypt and Ireland, where the plane was registered, as well as representatives from Airbus, which manufactured it.
The plane was given a clean bill of health in its annual review earlier this year, and airline officials insist there were no complaints about it before the flight.
All of which, notes Pizzey, is cold comfort to relatives and friends of victims, who have been showing selfies and holiday photos e-mailed just before the plane took off on its way home.
Analyses of the of the black box recorders, and a thorough recovery and examination of debris, could take a month or more according to Egyptian and other officials.