A diver lifts a fragment of a plane outside in Sochi, Russia on Dec. 28, 2016. (Emergency Situations Ministry Photo via AP)

Russian investigators said Thursday that there was probably no bomb blast aboard a military jet that crashed Sunday off the Black Sea coast, as they revealed new details from flight recorders recently retrieved from the wreckage.

The three-engine Tu-154, flying to Syria from the southern Russian city of Sochi, crashed shortly after takeoff, killing all 92 aboard. Why it went down remains a mystery, although Russian officials are leaning toward accidental causes, such as mechanical problems or pilot error, rather than an act of sabotage.

“It is clear that there was a technical malfunction,” Transport Minister Maxim Sokolov said during a briefing in Moscow. “What caused it remains to be explained by the experts.”

More than a year after Russia first deployed military aircraft and special forces in Syria, blowback in the form of a terrorist attack has become a growing concern. Investigators said Thursday that the information revealed by the flight recorders has not eliminated the possibility the crash was caused by a terrorist attack, although it has made it less likely.

“We arrived at the conclusion that there was no explosion aboard,” Sergei Bainetov, head of the Russian armed forces’ flight safety service, said at a briefing in Moscow. “However, a terror attack does not have to be an explosion. Other causes are possible. Hence, we have not ruled out this theory for now.”

Bainetov also said that an analysis of the pilots’ remarks before the crash indicated an “emergency situation” on board, but he did not elaborate. 

Earlier, the Russian tabloid Life, which is close to the security services and regularly obtains surveillance camera footage after accidents, said the captain yelled “the flaps!” and a string of profanities shortly before the plane crashed. The flight was in the air for a total of 70 seconds and reached an altitude of 820 feet, Bainetov said Thursday.

Sokolov said 19 bodies, along with 230 body parts, have been retrieved by divers at the crash site.

Tu-154 jets, which have been in service for 33 years, were once the workhorse of the commercial airline industry here and are still widely used by government ministries.

It has been involved in serious crashes in Russia and abroad in recent years. Most significantly, a Tu-154 carrying Polish President Lech Kaczynski and other senior Polish officials crashed in 2010. No one survived.

Russia’s intervention in the Syrian conflict has made the country a target for terrorism. An Islamic State affiliate in Egypt asserted responsibility for a bombing aboard a Russian passenger jet in 2015 that killed 224 people, mostly vacationers returning from resorts in the Egyptian city of Sharm el-Sheikh

Last week, Russia’s ambassador to Turkey, Andrei Karlov, was fatally shot at a public event in an art gallery in downtown Ankara. The assassin, a 22-year-old police officer named Mevlut Mert Altintas, shouted, “Don’t forget Aleppo, don’t forget Syria,” moments after the killing.

The attacks have done little to change Russia’s policy in Syria or cause a rollback of its military deployment there. Russia has sought to strengthen its cooperation with Turkey in Syria despite Karlov’s killing as the Kremlin hammers out a coalition without the United States that can determine the fate of the conflict.

Since the attack on the jet in Egypt, Russia has widened its footprint in Syria, deploying new aircraft, special forces ground troops and the country’s sole aircraft carrier, the Admiral Kuznetsov, to the region.