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Investigators from around the world are trying to learn more about what happened to that Ukrainian airliner that crashed in Iran on Wednesday. A team from Ukraine is on the ground in Tehran, and earlier today U.S. officials said they were willing to grant travel waivers to Western investigators visiting the crash site. As NPR's Geoff Brumfiel reports, there is growing public evidence that a missile hit the plane. And a warning to our listeners - this piece contains the sound of an explosion that could be the plane.
GEOFF BRUMFIEL, BYLINE: Ukraine International Airlines Flight 752 got off to a routine start. It took off from Tehran International Airport just after 6 a.m. and turned northwest towards its destination.
ARIC TOLER: It got, you know, eight or so thousand feet up in the air, and then it disappeared off of the radar.
BRUMFIEL: Aric Toler is a researcher with Bellingcat, an independent group that conducts investigations using online tools. He says there are clues in videos and images that are popping up on social media - in particular, one video recorded from a construction site. It shows flickering dots above a block of apartment buildings.
TOLER: You can see there's kind of, like, these two lights, right? One comes and hits the other, and it's like an explosion.
(SOUNDBITE OF EXPLOSION)
BRUMFIEL: Toler and his team looked at features appearing in video - the apartment buildings, a water tank, a small structure in the foreground.
TOLER: And all these things put together, you can find out exactly where this video was filmed.
BRUMFIEL: It turns out to be a small town just a few miles away from the flight path, and the vantage point offers a clear view of what looks like a missile traveling up and hitting the plane. The next question is, where would a missile have come from? Fabian Hinz is an Iran specialist at the Middlebury Institute. He says the area north of the airport where the plane was flying is full of military sites - ammunition bunkers, a barracks.
FABIAN HINZ: Also quite a few sensitive military installations related to the IRGC, the Islamic Revolutionary Guards.
BRUMFIEL: The Islamic Revolutionary Guard Corps was the branch of the Iranian military responsible for attacking air bases in Iraq that same night. The facilities the plane was flying by include a missile research center that could have been a target for an American counter-strike.
HINZ: The Iranians have been very clear that they were preparing for American retaliation, and in such a situation, usually, your air defense systems would be on high alert.
BRUMFIEL: Hinz believes in air defense battery accidentally fired on the plane. Iran categorically denies a missile hit the flight and is investigating possible technical problems. Aric Toler finds that idea unlikely.
TOLER: Seems like a technical failure is kind of a cosmic coincidence - right? - to happen at the same time as all this geopolitical turmoil.
BRUMFIEL: Western intelligence agencies may have satellite images, radar data and intercepted communications that could aid the investigation. It remains to be seen how much of that will become public in the weeks and months ahead.
Geoff Brumfiel, NPR News, Washington. Transcript provided by NPR, Copyright NPR.