Canadian Prime Minister Justin Trudeau and other Western leaders say evidence suggests that an Iranian missile downed the Ukrainian passenger plane that crashed near Tehran.
"We have intelligence from multiple sources, including our allies and our own intelligence. The evidence indicates that the plane was shot down by an Iranian surface-to-air missile," Trudeau said on January 9.
"This may well have been unintentional," he told a press conference, calling for a "complete and credible investigation" into the cause of the crash.
Earlier, unidentified U.S. officials said they were confident that Iranian air-defense systems downed the Boeing 737-800, based on satellite, radar, and electronic data.
Iran has ruled out a missile strike as the cause of the crash, saying such a scenario makes "no sense" and it called on Canada to share any intelligence indicating that Iran had shot down the plane.
Ukraine International Airlines flight PS752 en route to Kyiv crashed on January 8 soon after taking off from the Iranian capital, killing all 176 people on board.
The victims included 63 Canadians, 82 Iranians, 10 Swedes, four Afghans, three Germans, and three Britons. There were also 11 Ukrainians on board, including nine crew.
The tragedy came hours after Iran fired missiles at bases housing U.S. forces in Iraq, prompting speculation that the plane may have been attacked.
Echoing Trudeau's words, British Prime Minister Boris Johnson later said in a statement, "There is now a body of information that the flight was shot down by an Iranian surface-to-air missile."
"This may well have been unintentional," Johnson added.
Earlier, U.S. President Donald Trump said he had "suspicions" about the crash, saying the plane "was flying in a pretty rough neighborhood and somebody could have made a mistake."
"Some people say it was mechanical. I personally don't think that's even a question," Trump said, adding that "something very terrible happened."
Ukraine's top security official, Oleksiy Danylov, earlier said the country was examining whether a missile strike brought down the aircraft.
Newsweek magazine quoted a Pentagon and a senior U.S. intelligence official, as well as an Iraqi intelligence official, as saying they believed the Ukrainian plane was hit by a Russian-made Tor missile.
CBS News, citing U.S. intelligence, said a satellite detected infrared "blips" of two missile launches, followed by another blip of an explosion.
The Pentagon declined to comment.
Iran's Transport Ministry said in a statement that "this story of a missile striking a plane cannot be correct at all."
"Several internal and international flights were flying at the same time in Iranian airspace at the same altitude of 8,000 feet (2,440 meters)," the ministry said.
"Such rumors make no sense," Ali Abedzadeh, the head of Iran's Civil Aviation Organization and deputy transport minister, said in the statement.
The Boeing crashed shortly after taking off from Tehran's Imam Khomeini airport.
The Civil Aviation Organization said on January 9 that initial evidence gleaned from eyewitnesses on the ground and in a passing aircraft showed that the Ukrainian plane was on fire and had turned back toward the airport before it crashed.
The crew flying the 3-year-old plane, which had its last scheduled maintenance on January 6, initially headed west to leave the airport zone, sent no distress signals, nor did they contact ground control, it said.
A video aired by Iran’s state broadcaster appeared to show the plane already on fire as it fell from the night sky.
Ukrainian investigators, 45 of whom arrived in Tehran on January 9, said that they were seeking to search debris at the crash site to help determine the cause.
Iran and Ukraine have agreed "to coordinate further actions of our investigation groups closely" to determine the cause of the crash, according to Ukrainian Foreign Minister Vadym Prystayko.
In a phone call with Ukrainian President Volodymyr Zelenskiy, his Iranian counterpart, Hassan Rohani, "stressed that Iran would provide the Ukrainian expert group with prompt access to all the necessary data," according to Zelenskiy’s office.
Johnson also spoke to Zelenskiy and called for "a full, credible, and transparent investigation into what happened," Downing Street said.
And Canadian Foreign Minister Francois-Philippe Champagne held a telephone conversation with Iranian Foreign Minister Mohammad Javad Zarif to stress Canada's desire to be a part of the investigation into the crash.
Canada broke diplomatic relations with Iran in 2012, and Italy normally acts as a proxy for communication between Ottawa and Tehran.
Amid tensions heightened by the killing of top Iranian general Qasem Soleimani in a U.S. air strike in Baghdad last week, Iran has said it will not give the plane’s so-called black box, which contains flight data and cockpit voice recorders, to either U.S. authorities, nor to representatives of American plane maker Boeing.
Tehran is not obliged to do so and under international aviation rules is expected to be the lead investigator, while Ukraine, as the country where the plane was registered, would participate.
As aviation authorities searched for answers after the crash, Ukraine observed a day of national mourning on January 9, with Zelenskiy saying the state was prepared to provide families who lost relatives in the accident “with all the help they need.”
He also cautioned that the disaster was "not a topic for social-media hype, sensationalism, or conspiracy theories."