TORONTO -- Prime Minister Justin Trudeau says Canada has intelligence that indicates that the plane that crashed in Iran Wednesday morning, killing all 176 people aboard, was shot down by an Iranian missile – possibly by accident.

“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. This may well have been unintentional,” the prime minister said Thursday afternoon at a news conference.

Ukraine Airlines flight PS752 crashed near Tehran shortly after taking off. Sixty-three of its passengers had Canadian passports, and many others were living in Canada as permanent residents or on visas.

The Transportation Safety Board of Canada that the agency has been invited by the Aircraft Accident Investigation Bureau of the Islamic Republic of Iran to visit the crash site.

“We have accepted this invitation and we are making arrangements to travel to the site,” the agency wrote in the statement. “The TSB will be working with other groups and organizations already on site.”

Trudeau described the missile as the “probable cause” of the crash but declined to elaborate on what evidence Canadian officials possess that led them to believe a surface-to-air missile was to blame. U.S. President Donald Trump has suggested that he also believes Iran was responsible for the plane going down.

Flanked by several senior government and defence officials, the prime minister said he had called for Iran to allow a full investigation into the crash.

“The families of the victims and all Canadians want answers. I want answers. That means closure, transparency, accountability and justice,” he said.

“This government will not rest until we get that.”

Speaking at a joint press conference later on Thursday, Foreign Affairs Minister Francois-Philippe Champagne and British Foreign Secretary Dominic Raab echoed Trudeau’s call for an in-depth investigation into the crash.

“This new information reinforces the need to have a thorough investigation into this matter,” Champagne said. “As the prime minister said today, Canadians have questions and they deserve answers. I would add to that that the world has questions and that the world expects answers.”

Before Trudeau met with reporters, Hasan Rezaeifa, the head of the Iranian investigation commission, denied that a missile had been involved in the crash. He told Iran's state-run IRNA news agency that "the topics of rocket, missile or anti-aircraft system is ruled out."

Trudeau said he had been in touch with several world leaders since the crash, including Prime Minister Mark Rutte of the Netherlands, whose government led the investigation into the 2014 crash of Malaysia Airlines Flight 17. He said he had also shared Canada’s intelligence with Ukraine's President Volodymyr Zelensky.

Canada and Iran have not had formal diplomatic relations since 2012, when Canada labelled Iran a state sponsor of terrorism.

Champagne said he talked to his Iranian counterpart about the crash on Wednesday night to make “the case that Canada had a legitimate case to access” the country to provide consular services.

“The response by the Iranian government, or the Iranian foreign minister was open, was encouraging,” Champagne said.

Champagne said Canada’s quick-reaction team needs to obtain a visa before entering Iran, but added he’s noticed accelerated action on the matter since his phone call with Iranian officials.

Trudeau said Thursday that Canada has pushed Iran to allow Canadian investigators to take part in the probe, and that Iran has shown an “openness” to doing so but has not officially assented. He said Canadian consular officials are being sent to Turkey with the hope they will be allowed into Iran to provide assistance.

When asked, the prime minister did not speculate on what Canada’s response would be if a missile strike is conclusively found to have caused the crash, saying he would wait for an investigation to happen before discussing any possible retaliation.

The plane’s black box, which could provide pivotal clues for investigators, remains in Iran. Trudeau said that Iran has agreed to grant Ukrainian investigators access to the box, but does not intend to let it out of the country.

In his second public speech since the crash, Trudeau said again that he is not prepared to rule out any possible cause of the crash and reiterated that his thoughts are with the families of those killed.

“[Today’s] news will undoubtedly come as a further shock to the families who are already grieving in the face of this unspeakable tragedy,” he said.

In an interview on CTV's Power Play, the former director of the Canadian Security Intelligence Service said the government would have concluded that the plane had been shot down after scouring all possible pieces of evidence collected from media reports, government intelligence – from allies or otherwise – and embassies on the ground in Iran.

“Satellite photography is pretty effective these days,” said Richard Fadden. “I can’t imagine the number of satellites that must have overflown the crash site.”

“By taking a look at a crash site, its dispersal, and how the metal looks, you can tell if there was a kinetic event within the aircraft or outside of the aircraft.”

Fadden added the surface-to-air missile Trudeau referenced is often operated automatically.

“Most of them are governed by a series of algorithms which tell them when they can and can’t fire,” he noted. “Presumably what happened was that intelligence fed into the missile control system was wrong. It didn’t acknowledge this was a civilian aircraft, and was fired.”

CRASH IN IRAN ‘WORST POSSIBLE’ LOCATION FOR CANADIAN INVOLVMENT

Paul Heinbecker, a former Canadian ambassador to the United Nations, told 鶹ý Channel that Canada’s dearth of diplomatic ties with Iran poses a serious problem when it comes to having a say in the investigation.

“The Iranians have accepted that we will send some consular officials and that will help, but this is about the worst possible consular situation you could imagine,” he said.

Heinbacker said the crash should pressure the Canadian government to reopen ties with Iran, regardless of how officials feel about the country.

“The point isn’t that we are -- by setting up an embassy -- approving of the behavior of the country concerned,” he said. “The point really is that we’re looking after our own interests and absent people on the ground… we’re not able to protect Canadian interests.”

With files from The Canadian Press