What We Know So Far About the Mysterious Russian Flight Crash

— -- Authorities have yet to determine how a Russian plane mysteriously disappeared and crashed less than 30 minutes after it took off from an airport in Egypt, early Saturday, killing all 224 people on board.

Here is the latest breakdown on the possible causes, the investigation and the Metrojet crash victims.

Possible Causes

The head of Russia's Interstate Aviation Committee, the agency investigating the crash, told journalists in Cairo Sunday the plane broke apart midair, but warned that it was "too early to state a cause for the plane's destruction."

Egyptian officials say there was no distress call.

The Russian airliner Metrojet is blaming an "external influence" as the cause of the crash.

Alexander Smirnov, deputy general director of Metrojet, said today the crash could not have been caused by a technical fault.

"The only explicable cause can be a mechanical impact on the aircraft," Smirnov said, adding "there is no possible combination of system failures that could lead to the aircraft breaking-up in midair.

"The plane's crew completely lost control over the aircraft as the disaster started to unfold," Smirnov added.

ABC News aviation consultant Col. Stephen Ganyard, a retired Marine fighter pilot, said it’s too early to rule out anything. “We don’t have any evidence that points us in one way or the other,” he told “Good Morning America” today.

A Link to Terrorism?

The head of the U.S. National Counterterrorism Center, Nick Rasmussen, said today the intelligence community so far has no information to corroborate any specific nexus to terrorism. But He emphasized that "it's an unfolding" situation.

U.S. National Intelligence Director James Clapper said, "We don’t have any direct evidence of any terrorist involvement, yet."

"ISIL in a tweet claimed responsibility for it," Clapper said, using the government’s acronym for ISIS. "There is a very aggressive ISIL chapter in the Sinai. But we really don’t know and I think once the black boxes have been analyzed ... then perhaps we’ll know more."

When asked whether ISIS has the ability to shoot down an airliner, Clapper said, "It’s unlikely, but I wouldn’t rule it out."

The plane's so-called black boxes are still being analyzed. The Russian minister said the boxes are in good condition.

The Victims

Russian state media reported that 140 bodies were transported today to St. Petersburg, Russia, where they will be identified by family members.

A second plane carrying the remaining victims will depart Cairo this evening.

Victims’ relatives gathered at a hotel close to the airport in St. Petersburg where the downed flight had been expected to land. Officials set up a reception center at the hotel, where distraught people sat stunned in the lobby areas, being attended to by grief counselors.

Investigators took DNA samples to help identify the dead.

Three days of mourning have been declared in Russia to honor the victims.