Russian Plane Crashes in the Sinai

Metrojet Crash: Final Bodies Flown Home to Russia

Did a bomb bring down Russian airliner in Egypt? 2:33

CAIRO, Egypt — The removal of bodies from the scene of the Metrojet crash was completed Tuesday as 28 bags containing victims' remains were flown to Russia for DNA testing, local aviation ministry sources said.

Suitcases and personal belongings were also collected by authorities. They will be DNA tested in Russia as officials seek to identify all 224 victims of Saturday's crash over northern Sinai.

The mystery over what caused the disaster deepened early Tuesday when Russian news agency TASS reported that investigators had found "elements" in the wreckage that were not part of an Airbus A321. The items have been taken for examination, it reported, citing unidentified sources in Cairo.

However, an adviser to Egypt's aviation minister denied the report.

Related: What Could Cause a Plane to Break-up in Midair?

A senior U.S. defense official told NBC News late Monday that an American infrared satellite detected a heat flash at the same time and in the same vicinity of the crash.

According to the official, U.S. intelligence analysts believe the flash could indicate some kind of explosion on the aircraft itself — either a fuel tank or a bomb — but that there's no indication that a surface-to-air missile brought the plane down.

That same infrared satellite would have been able to track the heat trail of a missile from the ground.

"The speculation that this plane was brought down by a missile is off the table," the official said.

Image: Russian plane crashes in Egypt with 224 aboard
Russian Emergency Minister Vladimir Puchkov and other officials at the Metrojet crash site. MAXIM GRIGORIEV / RUSSIAN EMERGE / EPA

Three investigators from Ireland — where the doomed Airbus A321 was registered by a leasing company — arrived in Egypt Tuesday to work alongside Russian, Egyptian and French experts.

Flight 7K9268 was at 31,000 feet when it crashed only 23 minutes after taking off from the Red Sea resort of Sharm el-Sheikh. It was bound for St. Petersburg.

James Clapper, the U.S. director of national intelligence, said that while there is no direct evidence of any terrorist involvement yet, it couldn't be excluded that the plane was brought down by ISIS extremists in the Sinai Peninsula. "It's unlikely, but I wouldn't rule it out," he told reporters in Washington.

Asked if a terrorist attack could be ruled out, Russian President Vladimir Putin's spokesman Dmitry Peskov said: "No versions could be excluded."

However, experts said investigators would also be focusing on a previous accident in which the aircraft suffered "serious damage" from a tail strike and was grounded for several months for repairs.

Metrojet Crash: Plane Involved in Previous Accident 14 Years Ago 1:58

Post-accident repairs in the same part of the plane have caused at least two other midair breakups, including the world's second-deadliest plane crash — in Japan in 1985.

"In the case of the Japan Airlines 747, the repair failed allowing pressurized air into the vertical fin or rudder of the airplane," former captain and NBC News aviation safety expert John Cox said. "It caused it to separate and they lost control of the airplane. This is something the investigators are going to look at very carefully. If you have an explosive type decompression due to a failed pressure bulkhead, it's going to cause a lot of damage at the back of the airplane."

The jet's 'black boxes' — its flight data recorder and cockpit voice recorder — were recovered and were being analyzed.

What's in a Black Box 0:43

"The downloading of the data from the flight data recorders is a reasonably simplistic process to get the data down," Cox said. "The more complex process is in the analysis."

Alastair Jamieson reported from London.