Justin Trudeau has vowed that his government will not rest until it has achieved justice for the 176 people who died when a Ukrainian passenger jet near Tehran – most of whom were traveling to Canada.

Speaking on Thursday, the Canadian prime minister called for a thorough investigation of the disaster as he endorsed mounting intelligence that the Ukrainian passenger jet was accidentally shot down by an Iranian anti-aircraft missile.

“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. “This may well have been unintentional.”

He said that evidence only strengthened the need for a full investigation into the disaster.

“It is now more important than ever to know exactly how this tragedy happens. Canadians want answers. That means transparency, accountability and justice,” he said. “This government will not rest until we get that.”

Iran has disputed reports it accidentally brought down the plane, and suggested mechanical failure and a fire onboard the aircraft was the cause of the crash.

News that the disaster may have been caused by a missile strike caused further distress for members of the Iranian community in Canada mourning the loss of friends and relatives.

“This is new and incoming disturbing information – but if true, I’m not surprised; especially given the actions of the Iranian regime,” said Payman Parseyan, the former president of Edmonton’s Iranian Heritage Society.

But Praseyan said that no amount of blame would bring back the victims. “We loved our community family and – whether the Iranian government was involved or not – they’re not coming home.”

Sixty-three Canadians were onboard the Boeing 737-800, operated by Ukraine International Airlines, when it crashed near Tehran on Wednesday. One hundred and thirty-eight of the passengers were destined for Canada, making the crash the country’s worst aviation disaster since the 1985 Air India bombing, which killed 268 citizens.

Victims included Mansour Esnaashary Esfahani, 29, a civil engineering doctoral student in Ontario who had flown to Iran in December to get married.