Ukraine officials have said that they suspect that their plane was shot down by a Russian made missile.
A team of 45 Ukrainian experts has arrived in Tehran, the Iranian capital to examine why the Ukrainian International Airlines plane plunged from the sky minutes after takeoff from Imam Khomeini International Airport.
The plane crashed on Wednesday killing all 176 passengers and crew on board.
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The plane was carrying mostly Iranians and Iranian-Canadians and USA officials say that the Iranian army might have accidentally shot down the plane.
According to the FlightRadar24 monitoring website, the plane was last seen on radar at 2,400 metres, hours after Tehran launched more than a dozen ballistic missiles at US facilities in Iraq.
Iran officials say that the plane caught fire and was trying to turn back but the crew did not call for help. They also dismiss allegations by the USA as illogical.
The crash happened amid rising tensions between the United States of America and Iran following the murder of Iranian Quds commander Qassem Soleimani by the USA.
More: Al Jazeera