Wednesday's (January 8) crash heightened international pressure on Iran after months of friction with the United States and tit-for-tat military strikes.
Washington killed an Iranian general last week in Iraq, prompting Tehran to fire at U.S. targets.
The United States and Canada, which had 57 citizens on board, had blamed an Iranian action for bringing down the aircraft.
Ottawa had told Iran that "the world is watching." On Twitter, Iranian Foreign Minister Mohammad Javad Zarif said the armed forces investigation showed the downing of the Boeing 737-800 was the result of "human error at time of crisis caused by U.S. adventurism (that) led to disaster." An Iranian military statement, announcing that a missile had struck the plane and expressing condolences to the victims, said the plane had flown close to a sensitive military site belonging to the elite Revolutionary Guards.