Earlier today, a Russian Airbus stalled out and plunged into the northern Sinai desert, killing all 224 people on the flight. Investigators say that the crew complained almost immediately of mechanical problems and asked for a course change, but was the cause mechanical failure — or something more sinister?

A Russian aircraft carrying 224 people, including 17 children, crashed Saturday in a remote mountainous region in the Sinai Peninsula about 20 minutes after taking off from a Red Sea resort popular with Russian tourists, the Egyptian government said. There were no survivors.

According to Adel Mahgoub, chairman of the state company that runs Egypt’s civilian airports, except for three Ukrainian passengers, everyone on board was Russian. An Egyptian Cabinet statement said the 217 passengers included 138 women, 62 men and 17 children. There were seven crew members aboard the 18-year-old Airbus 321-200.

A senior aviation official said the pilot had radioed that the aircraft was experiencing technical problems shortly before air traffic controllers lost contact with the plane.

The Russian Embassy in Cairo said on its Twitter account that there were no survivors. Russian investigators were searching the Moscow offices of Metrojet, the company that owned the plane chartered by St. Petersburg-based Brisco tour agency.

It didn’t take long for Islamic State terrorists to claim responsibility for the downing:

A militant group affiliated to Islamic State in Egypt claimed responsibility for the downing of a Russian passenger plane that crashed in Egypt’s Sinai peninsula on Saturday, the group said in a statement circulated by supporters on Twitter. …

“The fighters of the Islamic State were able to down a Russian plane over Sinai province that was carrying over 220 Russian crusaders. They were all killed, thanks be to God,” the statement circulated on Twitter said.

They were hardly crusaders; the passengers, all but three of them Russian (the others Ukrainian) were tourists leaving the resort town of Sharm el-Sheikh at the southern end of the Sinai Peninsula. The claim of responsibility seems almost as far-fetched. The plane had reached a cruising altitude of 31,000 feet, above the altitude where hand-held SAMs can work. Terrorist groups in the Sinai are not known to have larger anti-aircraft systems, such as the Buk system used by Russian-backed rebels in eastern Ukraine to shoot down a Malaysian Air flight. It’s possible that they have that technology, but the circumstances and the earlier complaint about mechanical trouble in the aircraft make equipment failure a much more likely cause.

Still, Air France and Lufthansa announced today that they will no longer overfly the Sinai, but the Russians are taking a closer look at other probabilities, including issues with jet fuel:

Russian officials say they have opened an investigation for gross negligence and safety violations that may have led to the crash. In a statement released Saturday afternoon, Russia’s Investigative Committee said it was searching the Moscow offices of the airline, Kogalymavia, which flies under the brand Metrojet, and the airline’s facilities at Domodedovo International Airport. Airline employees would be interviewed and the quality of fuel used by Metrojet on its flights would be looked at.

Still, Air France-KLM and German carrier Lufthansa both said Saturday that they would avoid flying over the Sinai Peninsula due to the unclear circumstances of the crash, the Reuters news agency reported.

The Metrojet airliner “disappeared” over Sinai shortly after takeoff, the Russian aviation agency said. Egyptian authorities said the plane was in the air for about 25 minutes and had reached 31,000 feet before it went down just after sunrise.

Despite the issues of terrorism in the area, Egyptian authorities are now at the crash site:

The Airbus A321, operated by Russian airline Kogalymavia under the brand name Metrojet, was flying from the Red Sea resort of Sharm el-Sheikh to St Petersburg in Russia when it went down in central Sinai soon after daybreak, the aviation ministry said.

“I now see a tragic scene,” an Egyptian security officer at the site told Reuters by telephone. “A lot of dead on the ground and many who died whilst strapped to their seats.

“The plane split into two, a small part on the tail end that burned and a larger part that crashed into a rockface. We have extracted at least 100 bodies and the rest are still inside,” the officer, who requested anonymity, said.

Egyptian and Russian authorities said it was too early to draw any conclusions about the cause of the crash.

It may be a long while before any definitive conclusion can be reached — and it may take a very large effort to keep the site secure long enough to recover the bodies of all the victims and conclude the investigation at the site of the crash.