Ukrainian experts who had arrived at the UIA Boeing 737-800 passenger jet's crash site near Tehran airport were the first to figure out what actually brought the plane down, says chief of the Kyiv Scientific Research Institute of Forensic Expertise, Oleksandr Ruvin, whose experts were part of a group of Ukrainian experts deployed in Iran in the immediate aftermath of the tragedy.

Ruvin says it was passengers and crew's personal belongings, as well as positioning of most of the aircraft's elements, that helped the experts determine the cause of the Boeing's crash.

"We found several tablets, the remains of mobile phones, bags with documents, and bank cards at the wreckage assembly site. In them, we saw the effect of striking elements and some other factor. Later, during the inspection of each aircraft detail, we determined and identified the spots where a missile or an explosive device directly hit the aircraft. We also laid out all the elements the way they were assembled on the plane. Then we understood what had happened, and how," he said.

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Ruvin said the experts had discovered the spots where they saw the strike of missile elements, and came to the corresponding conclusion as early as January 10.

"Representatives of the Iranian authorities saw this, many officials arrived, they looked with us and asked to cover everything, not to film anything on mobile phones, and said they would deal with this 'tomorrow'. We agreed that we would arrive tomorrow morning, at 09:00. But they let us to the site only after 11:00 – there were no officials there anymore, it had already been officially announced by then that the plane had been shot down by a missile from the TOR-M1 complex of the Iranian Air Force," Ruvin said.

In addition, he said the crash site had not been properly guarded: "We saw a lot of strange people at the crash site... Iranians who collected stuff, debris. Someone took it for scrap and someone kept it."

As UNIAN reported earlier, Kyiv-bound UIA flight PS752 crashed shortly after takeoff from Tehran's Imam Khomeini International Airport in the early hours of Wednesday, January 8. It was carrying 167 passengers and nine crew members on board. Two passengers and the crew members were Ukrainians. There were also 82 citizens of Iran, 63 citizens of Canada, 10 citizens of Sweden, four citizens of Afghanistan, three citizens of Germany and the United Kingdom each. There were no survivors.

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On January 11, Iranian President Hassan Rouhani officially admitted that the Ukrainian airliner had been shot down by accident as a result of a "human error."