Investigators in Iran claimed on Thursday the black boxes of a Ukraine International Airlines (UIA) flight out of Tehran that crashed as Iran shot over a dozen missiles at Iraqi military bases housing U.S. troops had their memories damaged.

Iranian officials had previously refused to hand the black boxes over to Boeing, the manufacturer of the airplane.

Ukrainian Airlines flight PS 752 crashed after taking flight en route to Kyiv. The crash killed 176 people on board, mostly Ukrainian, Iranian, and Canadian citizens.

The preliminary report from Iran’s Civil Aviation Organization stated that search crews recovered both black boxes – in-flight recorders used to document the last moments of a flight in the event of a crash – and that they had successfully recovered cockpit communications and other data. The crash, the agency said, damaged some of the memory, however, meaning the information recovered is allegedly incomplete.

The Iranian report blamed the crash on an unknown “sudden technical issue” the set the plane on fire midair, according to the Ukrainian news agency UNIAN. It concluded that the pilots tried to turn the plane back to Tehran’s international airport shortly after takeoff but failed to do so successfully. The pilots, it stated, never tried to contact the control tower to report any issues.

UNIAN noted that the report did not discuss the potential of the missile assault on American targets catching the commercial airliner in its crossfire. It dismissed “electromagnetic interference” as a cause, which few had suggested as a likely culprit.

Following the release of the report, Iranian Civil Aviation Organization head Ali Abedzadeh issued a statement inviting the affected countries to “participate in the crash investigation and appoint their own special groups.” Abedzadeh had previously insisted that Iran would not hand over the black boxes “to the manufacturer [Boeing] and the Americans.”

Immediately following the crash, Iranian officials declared that mechanical failure was to blame, despite the lack of time for investigating the crash site. While Ukrainian officials did not object to this initially, they later urged caution in declaring a definitive cause behind tie fire.

Ukraine International Airlines later issued a statement calling the doomed plane “one of the best planes we had” and noting it had completed scheduled maintenance on Monday, suggesting something other than technical failure was involved. The airline also praised the crew, implying human failure was also unlikely.

The Internal Affairs Ministry of Ukraine announced Thursday that a national team had taken flight to Iran for investigations on the ground, including DNA sampling to confirm the identities of those on board. The Ukrainian team will also seek signs of any human error or violation of safety standards from the wreckage and compare results with the Iranian report.

The Ukrainian government has stated its suspicion that Iranians using Russian missiles shot down the plane, calling it a “main” theory.

“A strike by a missile, possibly a Tor missile system, is among the main (theories), as information has surfaced on the internet about elements of a missile being found near the site of the crash,” Oleksiy Danilov, secretary of Ukraine’s Security Council, told reporters, according to the Associated Press. Iran has boasted of possessing a Russian Tor missile system in government parades and did not address the potential use of missiles in its report on the crash. Danilov added, however, that he made “no claim” of proof that missiles were involved.

The U.K. Times noted that Danilov did not specify what on the internet had surfaced to suggest the missile attack, but “pictures emerged overnight of part of a Russian Tor M1 missile lying on a wall, apparently near the crash site.” Iran has denied the legitimacy of the images.

Ukraine’s president, Volodymyr Zelensky, urged Ukrainians not to indulge “conspiracy theories” in light of the crash, without addressing any in particular.

“Now our information space is filled with numerous theories and speculations about the tragedy. It is clear that we all want to know the truth as soon as possible. But in such cases, speed can interfere with the truth. We need to wait for at least the preliminary report of the investigation commission,” Zelensky said in a national address on the crash, calling it “not a topic for social media hype, sensationalism or conspiracy theories.”

“We need patience, endurance and wisdom. This scary story should teach all of us — and every citizen of Ukraine and every world leader — to appreciate human life,” he said.

In Canada, leftist Prime Minister Justin Trudeau demanded Canada take a prominent role in the investigation of the crash, given that 63 of those killed were Canadian citizens and 138 were scheduled to take a connecting flight into Canada.

“Canada is one of a handful of countries with a high degree of expertise when it comes to these sorts of accidents and therefore we have much to contribute,” Trudeau said in public remarks. “I am confident that in our engagement both through our allies and directly, we are going to make sure that we are a substantive contributor to this investigation.”

UNIAN, the Ukrainian news service, published a video allegedly shot on CCTV of the plane falling currently circulating on social media. “The footage shows what appears to be a series of bright flashes and then burning debris flying at a great speed as the airliner hits the ground,” the outet noted. UNIAN did not note the origin of the video or confirm its legitimacy.

Video shows Boeing 737 with 180 people on board on fire, crashing near Tehran Iran 🇷.#URGENTE Boeing 737 Ucraniano se estrella en Teheran #Iran pic.twitter.com/t8Wgpo3wVr — Nellie Belén Izarza 🌹 🇻🇺🇸 (@myteks) January 8, 2020

Ukraine banned all flights from Iranian airspace in the aftermath of the crash.

Ukraine has been embroiled in a war with Russia, Iran’s closest ally, for years. Russia annexed Ukraine’s Crimean peninsula in 2014 and maintains an ongoing presence, through pro-Russian paramilitaries, in the Donbas region, on the eastern border with Russia.

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