KYIV -- Ukrainian officials said on January 10 that they were focusing in particular on a missile strike or act of terrorism as two possible causes of the crash of a Ukrainian passenger airliner after takeoff from Tehran's international airport, adding that they wanted to establish an international coalition to conduct an investigation into the January 8 tragedy.
The head of the Ukrainian Security Service (SBU), Ivan Bakanov, told a press briefing that the missile strike and terror scenarios merited particular attention.
“I can assure you that we will surely inform the public of all objective, verified information," he added.
Ukrainian Foreign Minister Vadym Prystayko had said earlier in the day that Ukrainian investigators had been given access to pieces of the body of the plane and specialists were analyzing various videos around the crash.
Prystayko said Ukrainian officials were not discarding any possible version of what might have happened and they had so far found no evidence of a terror attack in fragments from the plane.
U.S., Canadian, and British officials have said it is “highly likely” that Ukraine International Airlines (UIA) Flight PS752 was shot down, possibly in error, by an Iranian missile. NATO's secretary-general and Dutch officials have also hinted at a similar conclusion.
All 176 people aboard were killed in the predawn tragedy.
Ukrainian President Volodymyr Zelenskiy said on January 10 that he had spoken to Canadian Prime Minister Justin Trudeau, whose country lost 63 people in the tragedy, and that "There should not be speculation about the tragedy. Ukraine and Canada will use all possible means to advocate for an objective and comprehensive investigation."
Prystayko said Ukrainian authorities have been given access to the black boxes that would have been collecting data of the Boeing 737-800's flight.
As for a possible terrorist attack, Bakanov said, "the topic is too important to draw any hasty conclusions.”
The air disaster came hours after Iran targeted two Iraqi bases that house U.S. troops with missiles on January 8 in response to a January 3 U.S. drone strike that killed Iranian Major General Qasem Soleimani in Baghdad.
Prystayko added in his press conference on January 10 that Ukraine has "no reason to say that the Iranian authorities do not want to work with Ukraine" in investigating the cause of the crash.
Iranian officials have said they will download data from the black boxes.
"We prefer to download the black boxes in Iran. But if we see that we can't do that because the boxes are damaged, then we will seek help," Iran's civil aviation chief, Ali Abedzadeh, told a news conference in Tehran on January 10. "One thing is for certain, this airplane was not hit by a missile."
Some videos have emerged from Iran that appeared to show an object or objects approaching an aircraft and an aircraft burning brightly well before impact with the ground.
WATCH: Investigator Explains Video Evidence
A crew from U.S. television network CBS said there were no security or investigators at the crash site when they arrived on January 10, and images were being shared that purported to show bulldozed earth at or near the scene of the disaster.
The Ukrainian-flagged plane was en route to Kyiv when it crashed.
On board were 63 Canadians, 82 Iranians, 10 Swedes, four Afghans, three Germans, and three Britons, in addition to 11 Ukrainians, including nine crew members.
Zelenskiy’s office said on January 10 that it was “too early on in the investigation to reveal specific details.”
Iranian officials have called on Western governments to share any intelligence or evidence suggesting Iran had shot the plane down.
Some have speculated that Iranian air defenses might have been on high alert and mistakenly responded to spotting the jet.
Prystayko said the plane "turned around after something happened [but it is] hard to say why."
If it turns out that Flight PS752 was shot down by a missile, Prystayko said, Ukraine will demand punishment of those responsible and compensation from Iran.
"We do believe that it’s likely that that plane was shot down by an Iranian missile," U.S. Secretary of State Mike Pompeo told a January 10 press conference at which he and Treasury Secretary Steven Mnuchin announced a fresh round of U.S. sanctions targeting eight senior Iranian officials and companies in the metals sector.
"We're going to let the investigation play out before we make a final determination," Pompeo said. "When we get results of that investigation, I am confident we and the world will take appropriate actions in response."
In a reversal from its earlier stance, Iran said on January 10 it had invited the U.S. National Transportation Safety Board (NTSB) and the U.S. manufacturer Boeing to participate in the investigation.
Boeing said on January 10 it was working with U.S. regulators to assist in the investigation of the crash. Under U.S. sanctions law, the U.S. Treasury must grant approval for U.S. investigators or the company to take part and potentially travel to Iran.
"Specialists must be given a chance to analyze the situation and make conclusions," Russian Deputy Foreign Minister Sergei Ryabkov said in Tokyo.
The sudden escalation follows more than a year of tightening U.S. sanctions under a "maximum pressure" policy aimed at changing Iranian behavior since U.S. President Donald Trump withdrew from a 2015 nuclear deal with Iran and other world powers to curb Tehran's nuclear activities in exchange for sanctions relief.