(CNN) How close are authorities to pinpointing what caused a Russian passenger jet to break up in midair and crash in Egypt's Sinai Peninsula?

That depends whom you ask.

The airline says technical faults or human errors couldn't have caused Metrojet Flight 9268 to crash.

An Egyptian soldier prays as emergency workers prepare to unload bodies of victims at a military airport north of Suez, Egypt, on October 31.

An Egyptian soldier prays as emergency workers prepare to unload bodies of victims at a military airport north of Suez, Egypt, on October 31.

Journalists and spectators wait for ambulances to arrive at the Zeinhom morgue in Cairo on October 31.

Journalists and spectators wait for ambulances to arrive at the Zeinhom morgue in Cairo on October 31.

Employees with the Russian Ministry for Emergency Situations wait in Moscow for their flight to Egypt on October 31.

Employees with the Russian Ministry for Emergency Situations wait in Moscow for their flight to Egypt on October 31.

People light candles and leave flowers at the Russian Embassy in Kiev, Ukraine, on October 31.

People light candles and leave flowers at the Russian Embassy in Kiev, Ukraine, on October 31.

Villagers watch an ambulance as it drives to unload bodies on October 31.

Villagers watch an ambulance as it drives to unload bodies on October 31.

The tail of the jet sits in a field on October 31.

The tail of the jet sits in a field on October 31.

An item of clothing lies at the site where the plane crashed on October 31.

An item of clothing lies at the site where the plane crashed on October 31.

Ismail, center, and other officials visit the site of the plane crash on October 31.

Ismail, center, and other officials visit the site of the plane crash on October 31.

Egyptian Prime Minister Sherif Ismail, third from right, visits the site of the plane crash with military and government officials on October 31.

Egyptian Prime Minister Sherif Ismail, third from right, visits the site of the plane crash with military and government officials on October 31.

Egyptian paramedics load the bodies of victims into a military plane at a military air base by the Suez Canal on Saturday, October 31.

Egyptian paramedics load the bodies of victims into a military plane at a military air base by the Suez Canal on Saturday, October 31.

People place flowers and messages in front of the Russian Embassy in Cairo on November 1.

People place flowers and messages in front of the Russian Embassy in Cairo on November 1.

Candles, toys, flowers and portraits are left at Pulkovo International Airport outside St. Petersburg on November 1.

Candles, toys, flowers and portraits are left at Pulkovo International Airport outside St. Petersburg on November 1.

Debris from the airliner is seen on November 1.

Debris from the airliner is seen on November 1.

More debris is shown on November 1. The crash site is in a remote area of a region plagued by a violent Islamic insurgency.

More debris is shown on November 1. The crash site is in a remote area of a region plagued by a violent Islamic insurgency.

Debris belonging to the Russian airliner is shown at the site of the crash on November 1.

Debris belonging to the Russian airliner is shown at the site of the crash on November 1.

Egyptian army soldiers guard the luggage and other belongings of passengers piled up at the site of the crash on November 1.

Egyptian army soldiers guard the luggage and other belongings of passengers piled up at the site of the crash on November 1.

A piece of the engine sits on the ground at the crash site on November 1.

A piece of the engine sits on the ground at the crash site on November 1.

Egyptian military personnel stand near the tail of the jet in Hassana on Sunday, November 1.

Egyptian military personnel stand near the tail of the jet in Hassana on Sunday, November 1.

Russian emergency personnel collect personal belongings of victims at the crash site in Hassana, Egypt, on November 2.

Russian emergency personnel collect personal belongings of victims at the crash site in Hassana, Egypt, on November 2.

People visit a makeshift memorial at the airport in St. Petersburg on November 3.

People visit a makeshift memorial at the airport in St. Petersburg on November 3.

The wreckage of Flight 9268 is seen in this image provided on Tuesday, November 3.

The wreckage of Flight 9268 is seen in this image provided on Tuesday, November 3.

The militant group ISIS published this image of what it claims is the bomb that brought down Metrojet Flight 9268 on Saturday, October 31. The photograph shows a soft-drink can and two components that appear to be a detonator and a switch. Flight 9268 crashed in Egypt's Sinai Peninsula en route to the Russian city of St. Petersburg. All 224 people on board were killed.

But Russian officials say it's too soon to tell what made the passenger jet plunge to the ground Saturday, killing all 224 people on board

Experts agree it's too early to know for certain, and officials have downplayed an apparent claim by Islamic militants that they brought down the Airbus A321-200, saying technical failure is the most likely reason for the crash.

Here's what we know so far:

THE FLIGHT

Flight 9268 was on its way from the Egyptian resort of Sharm el-Sheikh to St. Petersburg early Saturday when it dropped off radar about 23 minutes into the flight, Egyptian officials say.

Air traffic controllers apparently didn't receive any distress calls.

"There was nothing abnormal before the plane crash," Egyptian Civil Aviation Minister Hossam Kamel said Saturday. "It suddenly disappeared from the radar."

The website Flightradar24, which tracks aircraft around the world, said it had received data from the Russian plane suggesting sharp changes in altitude and a dramatic decrease in ground speed before the signal was lost.

THE CRASH

A U.S. satellite that was over Sinai at the time of the crash detected a heat flash, according to a U.S. official directly familiar with the latest information in the investigation. U.S. intelligence and military officials are analyzing the data to determine whether the flash occurred in midair or on the ground and what that can tell them about what happened to the plane, the official said.

Analysts say heat flashes could be tied to a range of possibilities: a missile firing, a bomb blast, a malfunctioning engine exploding, a structural problem causing a fire on the plane or wreckage hitting the ground.

"The number of heat signatures is crucial," said CNN aviation analyst Miles O'Brien. "If, in fact, only one was detected, that in some respects might steer one away from a missile launch and onto some idea of an explosion onboard the aircraft."

Alexander Smirnov, a Metrojet official, told reporters in Moscow on Monday the airline had ruled out technical problems and human error. Protection systems on the plane would have prevented it from crashing, he said, even if there were major errors in the pilot's control equipment.

Photos: Russian plane crashes in Egypt Photos: Russian plane crashes in Egypt The militant group ISIS published this image of what it claims is the bomb that brought down Metrojet Flight 9268 on Saturday, October 31. The photograph shows a soft-drink can and two components that appear to be a detonator and a switch. Flight 9268 crashed in Egypt's Sinai Peninsula en route to the Russian city of St. Petersburg. All 224 people on board were killed. Hide Caption 1 of 25 Photos: Russian plane crashes in Egypt The wreckage of Flight 9268 is seen in this image provided on Tuesday, November 3. Hide Caption 2 of 25 Photos: Russian plane crashes in Egypt People visit a makeshift memorial at the airport in St. Petersburg on November 3. Hide Caption 3 of 25 Photos: Russian plane crashes in Egypt Trucks in St. Petersburg carry victims' bodies on Monday, November 2. Hide Caption 4 of 25 Photos: Russian plane crashes in Egypt Russian emergency personnel collect personal belongings of victims at the crash site in Hassana, Egypt, on November 2. Hide Caption 5 of 25 Photos: Russian plane crashes in Egypt Egyptian military personnel stand near the tail of the jet in Hassana on Sunday, November 1. Hide Caption 6 of 25 Photos: Russian plane crashes in Egypt A piece of the engine sits on the ground at the crash site on November 1. Hide Caption 7 of 25 Photos: Russian plane crashes in Egypt Egyptian army soldiers guard the luggage and other belongings of passengers piled up at the site of the crash on November 1. Hide Caption 8 of 25 Photos: Russian plane crashes in Egypt Debris belonging to the Russian airliner is shown at the site of the crash on November 1. Hide Caption 9 of 25 Photos: Russian plane crashes in Egypt More debris is shown on November 1. The crash site is in a remote area of a region plagued by a violent Islamic insurgency. Hide Caption 10 of 25 Photos: Russian plane crashes in Egypt Debris from the airliner is seen on November 1. Hide Caption 11 of 25 Photos: Russian plane crashes in Egypt Debris at the crash site on November 1. Hide Caption 12 of 25 Photos: Russian plane crashes in Egypt Candles, toys, flowers and portraits are left at Pulkovo International Airport outside St. Petersburg on November 1. Hide Caption 13 of 25 Photos: Russian plane crashes in Egypt People place flowers and messages in front of the Russian Embassy in Cairo on November 1. Hide Caption 14 of 25 Photos: Russian plane crashes in Egypt Egyptian paramedics load the bodies of victims into a military plane at a military air base by the Suez Canal on Saturday, October 31. Hide Caption 15 of 25 Photos: Russian plane crashes in Egypt Egyptian Prime Minister Sherif Ismail, third from right, visits the site of the plane crash with military and government officials on October 31. Hide Caption 16 of 25 Photos: Russian plane crashes in Egypt Ismail, center, and other officials visit the site of the plane crash on October 31. Hide Caption 17 of 25 Photos: Russian plane crashes in Egypt An item of clothing lies at the site where the plane crashed on October 31. Hide Caption 18 of 25 Photos: Russian plane crashes in Egypt The tail of the jet sits in a field on October 31. Hide Caption 19 of 25 Photos: Russian plane crashes in Egypt Villagers watch an ambulance as it drives to unload bodies on October 31. Hide Caption 20 of 25 Photos: Russian plane crashes in Egypt People light candles and leave flowers at the Russian Embassy in Kiev, Ukraine, on October 31. Hide Caption 21 of 25 Photos: Russian plane crashes in Egypt A relative reacts to news at Pulkovo International Airport on October 31. Hide Caption 22 of 25 Photos: Russian plane crashes in Egypt Employees with the Russian Ministry for Emergency Situations wait in Moscow for their flight to Egypt on October 31. Hide Caption 23 of 25 Photos: Russian plane crashes in Egypt Journalists and spectators wait for ambulances to arrive at the Zeinhom morgue in Cairo on October 31. Hide Caption 24 of 25 Photos: Russian plane crashes in Egypt An Egyptian soldier prays as emergency workers prepare to unload bodies of victims at a military airport north of Suez, Egypt, on October 31. Hide Caption 25 of 25

"Therefore the only reason that could explain the plane's breaking up in the midair can be a certain impact, a purely mechanical (and/or) physical impact on (the) flying vessel," he said.

The vague comment made translation difficult, with some interpreting that the executive said an "external influence" caused the crash.

The head of the Russian Federal Air Transport Agency, however, quickly pushed back.

"It is completely premature to speak about the reasons of this, as there are not grounds. And I'd like to call on the aviation community to refrain from any premature conclusions," Transport Agency chief Alexander Neradko told the state-run Russian news agency Sputniknews.com

Learning that the plane broke into pieces while in the air helps reduce the list of possible causes of the crash, but there are still plenty of scenarios, said CNN aviation analyst Peter Goelz.

"It narrows it down a little bit, but there are a number of issues that could have affected this plane," said Goelz, a former managing director of the U.S. National Transportation Safety Board, or NTSB. "And terrorism has not been ruled out."

He suggested the disaster could have resulted from "some sort of catastrophic failure, perhaps caused by an earlier maintenance problem. It could have been a center fuel tank that might have exploded."

THE PLANE

The A321-200 was built in 1997, and the airline company Kogalymavia, which flies under the name Metrojet , had been operating it since 2012, Airbus said. The aircraft had clocked around 56,000 flight hours over the course of nearly 21,000 flights, the plane maker said.

And so far, officials have said all its inspections were in order.

The aircraft passed a routine inspection before takeoff, Egyptian Airports Co. chief Adel Al-Mahjoob said Saturday.

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According to the Aviation Safety Network , which tracks aircraft incidents, the same plane's tail struck a runway while landing in Cairo in 2001 and required repair. At the time, the aircraft was registered to the Lebanese carrier Middle East Airlines, registration records show.

Kogalymavia's Andrei Averyanov said the plane had been damaged in 2001, but had most recently been thoroughly checked for cracks in 2013. Not enough time had passed for major cracks to develop to a critical size since then, he said.

Smirnov said that he had personally flown the plane in recent months and that it was "pristine."

THE VICTIMS

There were 217 passengers and seven crew members on board Flight 9268. Of the passengers, 209 were Russian, four were Ukrainian and one was Belarusian. The citizenships of three other passengers are unknown.

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Russian media reported that the disaster created a large number of orphans in Russia, as a lot of parents left their young children with relatives while they took vacations in Sharm el-Sheikh.

Most of the bodies retrieved at the crash site are intact, a medical source in Sinai told CNN on Monday, and showed no major burns.

The photo of 10-month-old Darina Gromova posted by the baby's mother before a family trip to Egypt.

So far, two flights carrying remains of victims have flown to Russia, according to the TASS news agency. The first flight carried 130 bodies and dozens of body fragments. It was unclear how many victims' remains were aboard the second flight, which landed in St. Petersburg early Tuesday.

THE INVESTIGATION

Egyptian President Abdel Fattah el-Sisi has promised Russian President Vladimir Putin that he will allow "the broadest possible participation of Russian experts in the investigation," according to the Kremlin, and Russian officials have joined their Egyptian counterparts at the crash scene. Putin has also ordered Russian Prime Minister Dmitry Medvedev to open an investigation, the Kremlin said.

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Aviation investigators from France and Germany, the countries where the plane was manufactured, are also taking part.

The aircraft's engines were manufactured in the United States. If the plane's engines become a focus of the investigation, the U.S. National Transportation Safety Board will likely dispatch a team to Egypt as well, a U.S official with knowledge of the investigation said.

The plane's black boxes , which were recovered at the crash site Saturday, have not yet been read or decoded, Smirnov said.

Photo released by Egypt's Ministry of Civil Aviation.

THE REGION

Sharm el-Sheikh, where Flight 9268 began its journey, is a beach resort dotted with palm trees at the southern tip of the Sinai Peninsula. The plane crashed about 300 kilometers (185 miles) farther north, near a town called Housna, according to Egyptian authorities.

The Sinai Peninsula has been a battleground between ISIS-affiliated militants and Egyptian security forces. The conflict has killed hundreds of people.

The militants appeared to claim responsibility for bringing down the Russian passenger jet in a statement posted online Saturday, but officials in Egypt and Russia disputed it.

Mahjoob, the airport official, said there was no evidence of a terrorist attack. And Russian Transport Minister Maxim Sokolov said the claim that terrorists brought down the plane with an anti-aircraft missile "cannot be considered reliable," according to RIA Novosti.

The Egyptian military said militants in Sinai have shoulder-fired, anti-aircraft weapons that shoot only as high as 14,000 feet, far short of the more than 30,000 feet at which Flight 9268 was flying when it dropped off radar.

Kremlin spokesman Dimitry Peskov refused to discount terrorism, telling CNN's Matthew Chance on Monday that "only (the) investigation can rule out something."

Metrojet executives also said Monday that it was too early in the investigation to speculate or draw any conclusions. But Smirnov referred to purported footage of the crash posted by militants, saying: "Those images you have seen on the Internet, I think they are fake."