Kiev - A top Ukrainian security official on Thursday set out what he said were the four main theories for why a Ukrainian airliner crashed in Iran the previous day killing 176 people, including a possible missile strike and terrorism.
Oleksiy Danylov, secretary of Ukraine's National Security and Defence Council, made his statement as an initial report by Iranian investigators said the plane, a Boeing 737-800, had been on fire immediately before it crashed.
Ukraine is looking at various possible causes of the crash, including a possible missile attack, a collision, an engine explosion or terrorism, he wrote in a Facebook post.
The crash happened hours after Iran launched missile attacks on US-led forces in Iraq, leading some to speculate that the plane may have been hit.
But an initial assessment by Western intelligence agencies was that the plane had suffered a technical malfunction and had not been brought down by a missile, five security sources - three Americans, one European and the Canadian - who asked not to be named, told Reuters.