TORONTO -- Prime Minister Justin Trudeau said most of the passengers on board a Ukrainian plane that crashed near Iran鈥檚 capital were headed to Canada.

Of the 167 passengers and nine crew members who were killed in the Ukraine International Airlines jet crash, Trudeau told reporters that 138 of them -- including 57 Canadians -- were scheduled to arrive in Toronto Wednesday afternoon on a connecting flight from Kyiv, Ukraine.

鈥淥n behalf of all Canadians, I would like to express my deepest condolences to those who are mourning the loss of a loved one,鈥 he told reporters. 鈥淵our loss is indescribable and this is a heartbreaking tragedy.鈥

鈥淎n entire country is with you. We share your grief.鈥

Flight PS752, a Boeing 737-800 aircraft, hurtled into farmland outside of Tehran, Iran only minutes after taking off from the capital鈥檚 main international airport on Wednesday morning.

Trudeau said he鈥檚 spoken with the leaders of France, the United Kingdom, the United States and Australia to discuss the matter.

鈥淭hey all expressed their deepest sympathies to the families and to all Canadians and offered to help and support,鈥 he added.

Ukrainian Foreign Affairs Minister Vadym Prystaiko said there were 63 Canadians, 82 Iranians, and 11 Ukrainians on board. There were also 10 Swedish, four Afghan, three German, and three British nationals killed in the crash.

The airline released a list of the passengers on board the plane which includes birth dates, but not nationalities. The youngest person on the flight was born in 2016, while the oldest was born in 1950.

In a statement released Wednesday, Prime Minister Justin Trudeau said he was 鈥渟hocked and saddened鈥 to learn of the plane crash in Iran.

鈥淪ophie and I offer our deepest condolences to those who have lost family, friends, and loved ones in this tragedy. Our government will continue to work closely with its international partners to ensure that this crash is thoroughly investigated, and that Canadians鈥 questions are answered. Today, I assure all Canadians that their safety and security is our top priority,鈥 he said.

Canada鈥檚 foreign affairs minister Francois-Philippe Champagne also released a statement following news of the plane crash.

鈥淚 was deeply shocked and saddened to learn that, according to preliminary reports, at least 63 Canadians were among the 176 people who were killed when Ukraine International Airlines Flight PS752 crashed after takeoff yesterday near Tehran, Iran. As more information becomes available, including regarding dual citizens, this number could change,鈥 he said.

鈥淚 would like to extend my deepest condolences to those who lost loved ones in this tragic event, including citizens of a number of other countries.鈥

Champagne added that he has been in touch with his Ukrainian counterpart and the Canadian government is committed to working closely with international partners on the investigation.

Anyone seeking information about Canadian citizens believed to be on board Flight PS752 was urged to contact Global Affairs Canada鈥檚 Emergency Watch and Response Centre at 1-800-387-3124 or by email at sos@international.gc.ca.

Transport Minister Marc Garneau said on Twitter his office was in touch with their international counterparts and that Canada is offering 鈥渢echnical assistance鈥 to the investigation.

The Transportation Safety Board of Canada . It has appointed an expert to review any information released by Iran and monitor the investigation.

The agency also said it is available to provide any assistance in the investigation.

Ukrainian President Volodymyr Zelenskiy also extended his condolences to the victims鈥 families. His office said he was cutting short a visit to Oman to return to Kyiv. Ukrainian officials have offered to assist with the investigation and announced they鈥檙e preparing to send a group of specialists to help determine the cause of the crash.

Andriy Shevchenko, Ukraine鈥檚 ambassador to Canada, 鈥 and they 鈥渨ill have to go through this terrible pain together with our Canadian brothers and sisters.鈥

Shevchenko added that Ukraine would welcome Canada鈥檚 help with the investigation.

鈥淭he investigation on the ground is conducted by Iran, and Ukraine will of course contribute," he said in an interview with The Canadian Press. "We're ready to do everything we can to help the investigation. We hope that the Canadian offer of contribution into the investigation will be recognized and appreciated."

Most of the passengers were en route to the Ukrainian capital, Kyiv, before making their way to other destinations, airline officials said. Staff at Boryspil airport in Kyiv told The Associated Press that Iranian students coming home after winter holidays usually make up the passengers on that flight.

Among the Canadian students on board included those from the University of Toronto, the University of Alberta, the University of Guelph the University of Manitoba, Western University, the University of Ottawa and Carleton University.

The University of Waterloo and McMaster University have also indicated that it appears a couple of their students were on the passenger list, though it鈥檚 not yet clear whether the students in fact boarded the flight.

The devastating crash happened hours after Iran launched a ballistic missile attack on two Iraqi bases housing American soldiers. Iran鈥檚 Supreme Leader Ayatollah Ali Khamenei said the strikes were in retaliation for the U.S. killing of Iranian top general Qassem Soleimani.

Trudeau condemned the Iranian missile attacks and said all Canadians stationed at the Iraqi bases are safe and accounted for.

鈥淲e continue to encourage a de-escalation of tensions and a dialogue in the region,鈥 he added.

Iranian officials said they suspected a mechanical issue was to blame for the plane crash. Ukrainian authorities initially agreed, but later backed away from that assessment, citing the ongoing investigation.

There is no indication at this stage whether the plane crash is connected to the missile attack earlier that day.

When asked if he could categorically say whether or not the plane was shot down, Trudeau said he couldn鈥檛 and indicated that it is 鈥渢oo early to speculate.鈥

鈥淥ur focus today is on the many, many families who are grieving and our focus in the days and weeks to come will be on answering the questions that they have and indeed we all have as to how this happened,鈥 he said.

Plane crash in Iran
Rescue workers search the scene where an Ukrainian plane crashed in Shahedshahr southwest of the capital Tehran, Iran, Wednesday, Jan. 8, 2020. (AP Photo/Ebrahim Noroozi)

In light of the escalating tensions between the U.S. and Iran, Global Affairs Canada warned against any 鈥渘on-essential鈥 travel to Iran due to the 鈥渧olatile security situation, the regional threat of terrorism and the risk of arbitrary detention.鈥 The agency said those who hold dual Canadian-Iranian citizenship were particularly at risk for being arbitrarily questioned, arrested and detained.

鈥淚ran does not recognize dual nationality and Canada will not be granted consular access to dual Canadian-Iranian citizens,鈥 the statement said. 鈥淐anadian-Iranian dual citizens should carefully consider the risks of travelling to Iran.鈥

Following the plane crash in Iran, Canada鈥檚 only air carrier in the region, Air Canada, rerouted its flights to 鈥渆nsure the security of its flights into and over the Middle East.鈥

Flight PS752 had been delayed from taking off from Imam Khomeini International Airport by nearly an hour and never made it above 2,400 metres in the air, according to data from the flight-tracking website FlightRadar24.

Garneau said satellite data shows the plane 鈥渢ook off in a normal fashion,鈥 but that the satellites quickly lost contact with the aircraft.

鈥(It鈥檚) suggesting something very unusual happened, but we cannot speculate at this point,鈥 he said. 鈥淭here are a number of possibilities at this point and we will have to wait to obtain more information.鈥

Iran plane crash
Bodies of the victims of a Ukrainian plane crash are collected by rescue team at the scene of the crash in Shahedshahr, southwest of the capital Tehran, Iran, Wednesday, Jan. 8, 2020. (AP Photo/Ebrahim Noroozi)

While it鈥檚 still unclear what caused the crash, Qassem Biniaz, a spokesman for Iran鈥檚 Road and Transportation Ministry, was quoted in the state-run IRNA news agency as saying a fire struck one of the aircraft鈥檚 engines and the pilot then lost control of the plane.

Ukraine International Airlines announced that it has suspended flights indefinitely to Tehran.

Hassan Razaeifar, the head of Iran鈥檚 air crash investigation committee, said it appeared the pilot was unable to communicate with air-traffic controllers in Tehran moments before the crash.

Boeing released a brief statement about the crash involving one of its aircraft.

鈥淭his is a tragic event and our heartfelt thoughts are with the crew, passengers, and their families. We are in contact with our airline customer and stand by them in this difficult time. We are ready to assist in any way needed.鈥

While Iranian authorities said the plane鈥檚 black boxes, which record cockpit conversations and instrument data, had been found, the semi-official Mehr news agency quoted the head of Iran's civil aviation organization as saying the black boxes would not be sent to Boeing for investigation. Like other airline manufacturers, Boeing typically assists with investigations involving their aircraft.

Garneau said the black box could have an oral recording of the conversations between personnel on the aircraft and the control tower, which could shed light on exactly what happened.

鈥淚t might contain other information on the intelligence side could be revealed in the days to come,鈥 he added. 鈥淭hat鈥檚 the information we are seeking to obtain.鈥