A family of four, and a newlywed couple who had travelled to Iran to get married were among the 63 Canadians killed when a Ukrainian passenger jet crashed early on Wednesday morning.

All 167 passengers and nine crew members were killed when the plane, which was destined for Kyiv, crashed shortly after takeoff from Tehran.

More than a third of them were Canadian, many of whom were travelling home after winter holidays.

Justin Trudeau, said on Wednesday afternoon that 138 of the passengers were connecting to a flight to Canada. “All had so much potential, so much life ahead of them,” the prime minister said.

The victims included four members of a wedding party, and another 24 Iranian Canadians from Edmonton, said Reza Akbari, the president of the city’s Iranian Heritage Society.

Arash Pourzarabi, 26, and Pouneh Gourji, 25, graduate students in computer science at the University of Alberta, had travelled to Iran for their wedding, Akbari said.

He told the Edmonton Journal: “It’s been a shock, I know some of these people in person, I had a chance to see them at different, parties, gatherings, I’m in shock. I can tell you pretty much every Iranian in Edmonton knew some of them. So it’s very devastating.”

Trudeau said his government would work closely with other countries to investigate the crash, Canada’s worst transport disaster after the 1985 Air India bombing, which killed 268 citizens.

Trudeau told reporters on Wednesday afternoon that victims’ families deserve answers over the crash, but he cautioned: “It’s dangerous to speculate on possible causes.”

“Know that all Canadians are grieving with you,” he said.

In a statement, Trudeau said he and his wife were “shocked and saddened” by the news. “On behalf of the government of Canada, Sophie and I offer our deepest condolences to those who have lost family, friends and loved ones in this tragedy.”

As passengers were slowly identified, the scope of devastation to the Canadian Iranian community became clear.

Payman Parseyan, a former president of the Iranian Heritage Society of Edmonton, said the death toll represented nearly 1% of the Iranian community in the city. “Absolutely terrible,” he tweeted.

Other Edmonton residents who died in the crash were husband and wife Pedram Mousavi, 47 and Mojgan Daneshmand, 43 – both professors at University of Alberta’s engineering faculty.

Daneshmand and Mousavi were award-winning professors who worked in wireless communication technology. The pair were travelling home with their two daughters Daria, 14 and Dorina, nine.

“We are in mourning today – our community has suffered a terrible loss,” Edmonton’s mayor, Don Iveson, said in a statement, adding that he was “heartbroken” by news of the fatal crash.

Several of the passengers onboard the flight were students, according to Iran’s ISNA news agency. Delaram Dadashnejad, 27, had just graduated with a certificate in English at Vancouver’s Langara College in September, according to the school’s convocation program.

Mari Foroutan, 37, a doctoral candidate at the University of Waterloo in Ontario, was studying remote-sensing technologies to better understand climate change.

Ghanimat Azdahri, a doctoral student at the University of Guelph, who studies applied human sciences, was in Iran over the holiday visiting family, according to the ICCA Consortium, a group which supports indigenous peoples around the world.

“We are in utter disbelief and heartbroken at the sudden loss of such a beautiful young life – a true force of nature, and one of the ICCA Consortium’s most cherished flowers,” the group said in a tribute posted to its website.

The University of Ottawa confirmed three of its students had been killed in the crash.

Also among the victims were Ontario residents Evin Arsalani, 30, and her husband Hiva Molani, 38. The couple were travelling to a wedding with their one-year-old daughter Kurdia, Arsalani’s sister told the CBC. “At this point I don’t care how it happened. All I care is that I lost my family members,” she said.

More than 210,000 residents of Iranian descent live in Canada, according to the country’s most recent census, making it one of the largest Iranian diasporas in the world.

Canada has suspended diplomatic relations with Iran, and closed its embassy in Tehran in 2012. In recent months, US sanctions have made it increasingly difficult and costly for residents to travel between Iran and Canada.

With no direct flights linking the two countries, many choose to travel via Kyiv as a relatively affordable – if indirect – alternative.

Iranian officials have stated they suspect mechanical issues were a factor in the crash. Ukrainian officials have declined to offer a cause while the investigation takes place.

Air Canada, the only Canadian carrier to operate in the region, has “altered its routes to ensure the security of its flights into and over the Middle East”.

The Canadian government urged citizens to avoid non-essential travel to Iran – especially dual nationals “due to the volatile security situation and the regional threat of terrorism” – but did not mention the crash in its statement.

“My heart is broken. We will have to go through this terrible pain together with our Canadian brothers and sisters,” tweeted Andriy Shevchenko, Ukraine’s ambassador to Canada.

“There are no words. 176 lives lost. 63 Canadians won’t be coming home,” the opposition New Democrat leader Jagmeet Singh tweeted. “These families deserve clear answers, but whatever the case, this is devastating.”