Trudeau cited Canadian and allied intelligence on the matter. His announcement backs up what Pentagon officials told Fox News, which was that the passenger plane was shot down by mistake by an Iranian anti-aircraft missile.
U.S. intelligence has led officials to believe the airliner was accidentally struck by a Russian-made surface-to-air missile, just hours after Iran fired more than a dozen ballistic missiles targeting two military bases housing American and coalition troops.
President Trump said he does not believe the crash could have been due to a technical error. "It was flying in a pretty rough neighborhood," he said. "Somebody could have made a mistake on the other side."
Iran, however, maintains that the crash was due to an engine issue. The plane was a Boeing 737-800, the predecessor to the now-grounded Boeing 737 Max, which was embroiled in controversy after two fatal crashes in 2018 and 2019. The model was then internationally grounded. Iran's head of civil aviation was quoted by the ISNA News Agency as saying Thursday that "scientifically, it is impossible that a missile hit the Ukrainian plane, and such rumors are illogical," according to Reuters.
Gen. Abolfazl Shekarchi, the spokesman of the Iranian armed forces, earlier denied a missile hit the airplane in comments reported Wednesday by the Fars news agency. He dismissed the allegation as "psychological warfare" by foreign-based Iranian opposition groups.
Ukrainian investigators are awaiting permission to examine the crash site and search for missile fragments.
Of the 176 who perished in the jetliner crash, at least 63 were Canadian. The plane also carried 82 Iranians and 11 Ukrainians. Many of the passengers were believed to be international students attending universities in Canada; they were making their way back to Toronto by way of Kiev after visiting with family during the winter break.
The Ukrainian International Airlines flight took off at 6:12 a.m. Wednesday from Tehran's Imam Khomeini Airport. It reached nearly 8,000 feet before something went wrong. “No radio messages were received from the pilot regarding unusual situations,” a report by Iran's Civil Aviation Organization said.
Eyewitnesses, including the crew of another flight passing above it, described seeing the plane engulfed in flames before crashing at 6:18 a.m., the report said.
Fox News' Greg Norman and Lucas Tomlinson contributed to this report.