A massive search for wreckage of the Russian Tu-154 military aircraft that crashed into the Black Sea Sunday morning continues, while investigators ruled out a terrorist attack behind the tragedy.
The jet plunged into the sea two minutes after takeoff from the resort city of Sochi, where it was refueled on its way from Moscow to Russia's Hmeimim air base in the Syrian port city of Latakia, presumably killing all 92 people on board.
Over 3,500 people, as well as 45 ships, 12 airplanes, 10 helicopters, three drones and several deep-submergence vehicles are currently participating in the search and rescue operation.
So far, 11 bodies and 154 fragments have been recovered, of which 10 bodies and 86 fragments were sent to Moscow by plane for identification, the Russian Defense Ministry said.
Two elements of the steering unit were retrieved, thanks to the serial numbers which confirmed their identity, the ministry's spokesman Igor Konashenkov said.
Searching for the black boxes of the downed plane would prove to be a tough task, as the Tu-154 was not equipped with a radio-signalling system when built in 1983, with strong currents and deep water complicating the search.
Talking about the black boxes, the Interfax news agency quoted Russian Airspace Forces Commander-in-Chief Viktor Bondarev as saying that they could be intact since the fin where they were placed is normally the least damaged part in an air accident.
Despite the absence of the black boxes, the Russian authorities have excluded a terrorist attack from the list of possible causes of the accident.
The Federal Security Service (FSB), Russia's security service agency, said that it has found "no indications or facts pointing at the possibility of a terror attack or an act of sabotage on board the plane."
The Tu-154 was under tight supervision, the FSB stated, adding that the chief pilot and the flight engineer personally monitored the refueling, and only two FSB officials ascended the plane during its stopover in Sochi.
Instead, the probe is now directed toward four possibilities: pilot error, low quality of fuel, a foreign object stuck in the engine or a technical fault, according to the FSB.
The exact causes have yet to be determined by investigators and a special commission of the Russian Defense Ministry, as Russian President Vladimir Putin has pledged a thorough investigation into the case.
Ninety-two people -- 84 passengers and eight crew members -- were aboard the plane. Most of them were members of the Alexandrov Ensemble, a renowned choir of the Russian Armed Forces, as well as nine Russian journalists. They were heading to the air base for New Year celebrations.
Russia held a nationwide day of mourning on Monday. Flags were flown at half-mast at the signature buildings and government workplaces in Moscow. People laid flowers in front of the Moscow headquarters of the Alexandrov Ensemble, which was established in 1928 and had won worldwide acclaim.
Vadim Ananyev, a soloist of the choir who had stayed behind to take care of a newborn, was grieving.
"I have known these people for 30 years. I know their wives and children. I feel terrible for the children and for all that I have lost," he was quoted as saying.
The crashed aircraft has spent 6,689 hours in flight, with the most recent technical maintenance conducted in September 2016.
The Tu-154 is a three-engine medium-range airliner produced by Tupolev. It is one of the fastest civilian aircraft in use and has been widely used in extreme Arctic conditions.
