Egyptian authorities began probing the cause of a Russian passenger-plane crash in the Sinai Peninsula that killed all 224 passengers and crew on board in what may be Russia's deadliest airline disaster.

Preliminary investigations indicate the plane, an Airbus 321 operated by Russia's Metrojet, went down due to a technical problem, the state-run Ahram Gate website said, citing Egyptian security officials. The plane had reached cruising altitude, crashing 23 minutes after taking off from Sharm el Sheikh, a popular Red Sea resort, according to Egypt's government. The black boxes have been found, Egyptian Prime Minister Sherif Ismail said.

The Islamic State, in a report picked up by Al Jazeera and by the Washington-based SITE Institute, claimed responsibility in reprisal for Russian airstrikes on Syria.

"It is technically difficult to target a plane on that level," Ismail told reporters, saying it's too early to give a reason for the crash. It's not clear that the Islamic State group in Sinai has weapons capable of downing aircraft at such a height. "We have no evidence that anything unusual was happening on the plane before it crashed."

Sinai Campaign

Russian Transportation Minister Maxim Sokolov said on state television that reports of a terrorist missile aren't credible.

Bodies are being recovered from the wreckage, spread over 6 to 8 square kilometers (2 to 3 square miles) in the remote Al Hassana area of central Sinai, about 50 kilometers south of Al-Arish. Egyptian security forces have been waging a fierce campaign in the area against militants who have pledged allegiance to Islamic State. Workers have moved 129 bodies from the crash site, Ismail said.

Islamic State's statement doesn't specify how the plane was downed and the local affiliate may have jumped the gun to take credit, Mokhtar Awad, an analyst at the Center for American Progress, a research institute in Washington, said by e-mail.

Flight Paths

Air France, the French unit of Air France-KLM Group, and Deutsche Lufthansa AG said they would avoid flying over the Sinai area until the cause of the crash is known. The choice of flight paths came under public scrutiny following the downing of Malaysia Airlines Flight 17 in July last year over eastern Ukraine, an area that some airlines skirted amid fighting between government troops and pro-Russian separatists. Investigators said the crash, which killed 298 people, was caused by a missile.

In its final seconds, the Metrojet plane was bucking wildly, abruptly climbing and descending before communication was lost, according to FlightRadar24.com, which tracks flight routes. The A321, which took off at 5:51 a.m. Cairo time heading for St. Petersburg, had reached a cruising altitude of 31,000 feet, Egypt's Civil Aviation Ministry said in an e-mailed statement.

No SOS

"We didn't receive any SOS signals from the plane," Hossam Kamal, the minister, told reporters.

After reaching about 31,000 feet, the plane leaped and then plunged back again, according to FlightRadar24. At times it dropped as fast as 6,000 feet per minute, only to reverse and climb even faster, repeating several times. As that happened, it slowed dangerously. About 24 seconds before losing contact, it dropped to 71 miles per hour from 470 miles, according to the data. Jetliners such as the Airbus 321 can't stay aloft at such a speed.

If the FlightRadar24 data correctly represents what the aircraft was doing, "it probably rules out sabotage," said Paul Hayes, director of air safety and insurance at Ascend Worldwide. "It's probably some sort of control problem."

Speed Loss

Most worrisome is data showing a loss of speed, according to John Cox, a safety consultant and former airline pilot. "That bothers me," he said. "I wonder, did they manage to get the airplane stalled?"

Two recent accidents occurred with Airbus aircraft climbing sharply before losing speed and falling. In June 2009, an A330 operated by Air France went down in the Atlantic Ocean and in December 2014, an A320 operated by AirAsia Bhd. crashed in the Java Sea.

The A320 family is Airbus's most popular plane, a single-aisle, twin-engine type that allowed it to create a global duopoly with Boeing Co. for large passenger aircraft. The A321 is the longest variant.

The plane, operated by Metrojet since 2012 and produced in 1997, had logged about 56,000 flight hours over the course of nearly 21,000 flights, according to a statement from Blagnac, France-based Airbus.

The pilot had sought permission to land at a nearby airport because of technical problems, Dubai-based Al Arabiya reported, citing unidentified people. The plane was checked before it took off and no technical malfunctions were found, state-run Middle East News Agency reported, citing Adel Mahgoub, head of the Egyptian Co. for Airports.

Metrojet isn't attributing the crash to human error, Interfax reported, citing Oksana Golovina from Tourism Holding & Consulting, which owns Kogalymavia, as the carrier is known in Russia.

Deadly Crashes

Russian President Vladimir Putin declared Sunday a day of mourning. Since the Soviet Union collapsed in 1991, there have been at least 100 deadly passenger plane crashes involving aircraft operated by Russian airlines that have killed more than 2,000 people, according to Aviation Safety Network data.

About a fifth of all tourists visiting Egypt come from Russia, making it the largest source of vacationers to the North African country. The tourism industry is already reeling since a 2011 uprising ousted the government, weighing on foreign-exchange earnings.

Egyptian President Abdel-Fattah El-Sisi ordered a swift probe in coordination with Russian authorities.

BEA, France's air safety authority, is sending two officials to the crash site and six Airbus investigators will go as well, according to an e-mailed statement. Russia and Germany are also sending people, BEA said.

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