U.S. intelligence officials have evidence that suggests the Ukraine International Airlines jetliner that crashed in Iran on Wednesday, killing 176 people, was downed by an Iranian missile by mistake, multiple officials told NBC News. An initial Iranian report released Thursday suggested a sudden emergency struck the Boeing 737 before it went down just moments after taking off from Imam Khomeini International Airport in Tehran. The report said the crew never made a radio call for help and were trying to turn back for the airport when the plane crashed. Investigators from Iran's Civil Aviation Organization have offered no immediate explanation for the disaster. President Donald Trump, when asked Thursday for his thoughts on what happened to the jet, said, "Well, I have my suspicions." Trump added: "It's a tragic thing. Because somebody could've made a mistake on the other side. ... It was flying in a pretty rough neighborhood, and somebody could, could've made a mistake." The plane was carrying 167 passengers and nine crew members from several countries, including 82 Iranians, at least 63 Canadians and 11 Ukrainians, according to officials. The jet crash came within hours after Iran fired missiles at two Iraqi bases housing U.S. forces on Wednesday at 1:20 a.m. local time. The missile strikes were Iran's retaliation against the U.S. for the drone attack on Jan. 3 that killed Iranian Gen. Qassem Soleimani. American authorities later reported there were no casualties from the Iranian attack on the airbases. Ukrainian President Volodymyr Zelenskiy pledged to discover the "truth" behind the crash and announced investigators from his country had arrived in Iran to assist in the probe. Ukraine's President Volodymyr Zelensky placing flowers at a memorial for the victims of the Ukraine International Airlines Boeing 737. The Ukrainian Embassy in Iran originally said that the crash was likely caused by an engine problem. It also ruled out terrorism or a rocket attack as possible causes. However, it later removed that information from its website and said the cause of the crash was under investigation. Eyewitnesses to the crash, including the crew of another passing flight, described seeing the plane engulfed in flames before it went down, the Iranian report said. The crash caused a massive explosion, likely because the aircraft had been fully loaded with fuel for the flight to Kyiv, Ukraine. Both of the so-called “black boxes” containing data and cockpit communications from the plane were recovered, though they were damaged, the report said. Eyewitnesses, including the crew of another passing flight, described seeing the plane engulfed in flames before crashing, the report said. A child's shoe at the scene of a Ukrainian airliner that crashed The crash caused a massive explosion, likely because the aircraft had been fully loaded with fuel for the flight to Kyiv, Ukraine. Both of the so-called “black boxes” containing data and cockpit communications from the plane had been recovered, though they had been damaged, the report added. Zelenskiy also said he planned to call Iranian President Hassan Rouhani about the crash and the investigation. “Undoubtedly, the priority for Ukraine is to identify the causes of the plane crash,” he said. “We will surely find out the truth.” Zelenskiy said the crash will be investigated by a committee created by Iran's civil aviation agency. He also cautioned against speculation and conspiracy theories while the investigation is ongoing. "I call on the international community, including Canada, to join the investigation," he added. Ukrainian officials, for their part, initially agreed with Iranian suspicions that the 3½-year-old plane was brought down by mechanical trouble, but later backed away from that and declined to offer a cause while the investigation is ongoing. A top Ukrainian security official said in a Facebook post Thursday that four main scenarios of what could have happened are being looked into, including an anti-aircraft missile strike, a collision with a UAV or unmanned aerial vehicle, an engine failure and an explosion inside the aircraft as the result of a terrorist act. The plane was carrying 167 passengers and nine crew members from several countries, including 82 Iranians, at least 63 Canadians and 11 Ukrainians, according to officials. The crash just before dawn scattered flaming debris and passengers’ belongings across a wide stretch of farmland. It also came shortly after Iran launched a ballistic missile attack against Iraqi military bases housing U.S. troops amid a confrontation with Washington over the killing of a top Iranian general in a drone strike last week. 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 Kyiv after visiting their families during the winter break. The flight also included a family of four and newlyweds. The passenger list included several teenagers and children, some as young as 1 or 2. “Know that all Canadians are grieving with you,” Canadian Prime Minister Justin Trudeau said, addressing the victims’ families. Jan. 9 was declared a national day of mourning in Ukraine. The disaster could further damage Boeing’s reputation, which has been battered by the furor over two deadly crashes involving a different model of the Boeing jet, the much-newer 737 Max, which has been grounded for nearly 10 months. Boeing extended condolences to the victims’ families and said it stands ready to assist. Senior U.S. investigative sources said Wednesday Boeing and U.S. government investigators likely won't be able to investigate the crash.