Russia’s top aviation official said Sunday that the Russian jetliner that crashed in the Sinai Peninsula, killing all 224 people aboard, broke up at a high altitude shortly after takeoff on Saturday, the Associated Press reports.

An investigation into the crash is ongoing, but the head of Russia’s federal aviation agency, Alexander Neradko, said that the widespread distribution of debris and fragments of wreckage from the Metrojet Airbus A321-200 indicates that it disintegrated at a very high altitude.

“All signs attest to the fact that the aircraft disintegrated in the air at a high altitude,” Neradko said, the BBC reports.

The jetliner, bound for St. Petersburg from Sharm el-Sheikh, a resort town on the Red Sea, dropped out of the sky 23 minutes after takeoff, from 31,000 feet. By midday on Sunday, 163 bodies had been recovered from an area of 6 square miles, according to the Egyptian government.

“We are all shocked. It was a good plane. Everything checked out in 35 minutes,” an Egyptian ground service official who inspected the aircraft before takeoff told the AP. He claimed that two Russians were also members of the inspection team.

According to the New York Times, much of the Sinai Peninsula is a closed military zone from which jihadist insurgent groups mount attacks against the Egyptian government—one of those groups is the Sinai Province of the Islamic State (previously known as Ansar Beit al-Maqdis), which issued a statement claiming that they had brought down the airplane in retaliation for Russia’s military involvement in Syria.

“Soldiers of the Caliphate were able to down a Russian airplane over Sinai province,” the group said. “It was carrying on board more than 220 Russian crusaders. O Russians and whoever is allied with you, know that you neither have safety in the lands of Muslims nor in the air, and that killing dozens every day...by the bombardment of your aircraft will bring calamity on you.”

Russian Transport Minister Maksim Sokolov said that there was no evidence that the plane had been targeted, the BBC reports.

Photo via AP Images. Contact the author of this post: brendan.oconnor@gawker.com.