The initial assessment of Western intelligence agencies is that a Ukrainian airliner that crashed in Iran on Wednesday was not brought down by a missile, said a Canadian security source.

The source, who declined to be identified, said the agencies believed the Boeing 737 had suffered a technical malfunction. The Ukraine International Airline jet crashed shortly after takeoff from Tehran, killing all 176 people on board.

The disaster occurred shortly after Iran launched a series of missile attacks against two military bases in Iraq that housed U.S. troops.

¡°The initial assessment of Western intelligence agencies is that the plane was not brought down by a missile. There is no evidence to suggest that,¡± said the source.

The agencies believe the most likely cause of the crash was a malfunction, the source added, saying there was some evidence one of the plane¡¯s engines had overheated.

Boeing said it had no additional comment. Earlier, the company said it was in contact with the airline and was ready to assist.

In July 2014 a Malaysia Airlines flight from Amsterdam to Kuala Lumpur was shot out of the sky over eastern Ukraine during a rebellion by Russian-backed separatists, killing all 298 people on board.