WASHINGTON — The Ukrainian jet that crashed this week after taking off from Tehran appears to have been downed by an Iranian surface-to-air missile.

Intelligence indicates the Iranian military accidentally shot down the Ukrainian airliner with a Russian-supplied anti-aircraft missile, according to a U.S. official who was not authorized to speak publicly. All 176 aboard the Boeing 737 were killed.

Ukraine International Airlines Flight 752 crashed early Wednesday local time, shortly after Iran launched16 ballistic missiles on Iraqi bases housing U.S. soldiers.Iran's attack was retaliation after the killing of one of its top officials, Gen. Qasem Soleimani, in a U.S. drone strike ordered by President Donald Trump that has drawn a mixed reaction from U.S. and world leaders.

U.S. intelligence sensors showed Iranian air-defense radar locked onto the passenger plane, the official said. Iran’s military then launched two SA-15 surface-to-air missiles and brought the plane down in a fiery crash.

It’s unclear if the Ukrainian airliner was mistaken as a threat by the Iranian military, the official said.

Canadian Prime Minister Justin Trudeau said he, too, believed a missile was the cause of the plane crash, citing intelligence reports. Some 63 Canadians were among those who died.

63 Canadians killed:What we know

'I lived for her':Husband of Iran plane crash victim mourns wife of 10 years

That missile firing could have been an accident, Trudeau said Thursday at a news conference. Still, a "full and credible" investigation is required.

Iran denied the allegations that the aircraft was brought down by an Iranian missile and called on the U.S. and Canada to share any information they have, Ali Abedzadeh, the head of the country’s national aviation department, told reporters at a news conference Friday.

Asked if the U.S. should share some of the blame for the plane crash, Trudeau, who has had a testy relationship with Trump, again emphasized the need for a thorough investigation.

Canada is working with Ukrainian crash investigators, Trudeau said. Iran is insisting the plane's cockpit and flight data recorders — the "black boxes" — be kept in its country, Trudeau said. But, he said, Iran has told Ukraine it will have access to the data.

Trump said Thursday he found the plane crash suspicious and that "somebody could have made a mistake on the other side."

Though at least one Iranian official had earlier cast doubt on whether U.S. officials would be allowed in the probe, the National Transportation Safety Board in the U.S. says it will be following international rules regarding aircraft accidents. Those rules allow it to appoint an accredited representative to the investigation, according to an official who was not authorized to speak publicly on the matter. Boeing said it will be supporting the NTSB in a probe.

POLL:Americans say Soleimani's killing made U.S. less safe, Trump 'reckless' on Iran

In Ukraine, Oleksiy Danilov, secretary of the National Security and Defense Council, said investigators were looking into claims that parts of a Russian-made, surface-to-air missile stocked by Iran had been found near the crash site.

The head of Iran's Civil Aviation Organization, Ali Abedzadeh, quickly moved to dispute any suggestion that it shot down Ukraine's commercial airliner, according to Iran state media. The Fars News Agency, citing Abedzadeh, said its missiles were not capable of reaching that altitude. Abedzadeh characterized the suggestion as "scientifically impossible."

In a preliminary crash report issued Thursday, Iran's civil aviation authority said the plane's crew never made a radio call for help and was trying to turn back to the airport when the plane went down. The plane apparently suffered engine failure, Iranian officials said.

Iran says engine failure:As early as Thursday, experts were skeptical

IHS Markit, a London-based research and intelligence firm, says publicly available air traffic data is "not consistent" with Iran's claim. The firm says flight data shows a normal ascent until the plane disappears at 8,000 feet.

"This is consistent with a catastrophic incident onboard the aircraft," the report said.

The evidence overwhelmingly points to a catastrophic event in midair, said Mary Schiavo, a former U.S. Department of Transportation inspector general. She said not only did the plane's crew not send out a distress call, the aircraft itself has the capability to report any mechanical issues. It did not.

“It’s clear that the aircraft did not send any problem messages back to the airline,” she said, adding that "the aircraft did not turn around. Any turn that people saw was the aircraft falling from the sky.”

Publicly available flight data show the aircraft turning to the right before it crashed. Schiavo, who's seen the data, said it's unlikely that the flight's crew had the chance to change course.

Iran attack:Iranian TV reports a different version of missile attack

It’s likely U.S. officials would have detected any missile in the area where the plane crashed, said Ed Coleman, chairman of the department of safety science at Embry-Riddle Aeronautical University in Prescott, Arizona. That could have been accomplished with a satellite, or a drone, he said.

“There are probably U.S. assets and other countries’ assets that they could monitor and pick that up,” Coleman said.

Ukraine has experience with this sort of crisis. A Malaysia Airlines jetliner was downed over eastern Ukraine in 2014, resulting in 298 deaths. The investigation showed it was destroyed by a Russian-made Buk surface-to-air missile fired from eastern Ukraine in an area held by pro-Russian rebels.

Ukraine became part of a four-nation team led by the Dutch that brought charges against four suspects after a five-year investigation. Those charged included three Russians and a Ukrainian.

Iran, too, has mourned military shootdowns of civilian jetliners. In 1988, the guided-missile cruiser USS Vincennes mistakenly shot down an Iran Air jet over the Persian Gulf shortly after its takeoff from Tehran.

Ukraine President Volodymyr Zelensky said a special commission's investigation of the crash is underway. Zelensky said he has asked the prime ministers of the UK, Canada, Sweden, and the president of Iran for any information that could move the probe forward.

"Ukraine is interested in finding the truth," he said. "I ask all our international partners, if you have any evidence to assist the investigation, please provide it."

Contributing: Kim Hjelmgaard and Curtis Tate, USA TODAY.