UPDATED STORY:  Dozens of Canadians were among the 176 people killed in a plane crash just minutes after taking off from the Iranian capital’s main airport, Ukraine’s minister of foreign affairs, Vadym Prystaiko, said 63 Canadians, 82 Iranians and 11 Ukrainians were on board – the Ukrainian nationals included two passengers and the nine crew. There were also 10 Swedish, four Afghan, three German and three British nationals.

The crash, which killed everyone on board, happened Wednesday morning hours after Iran launched a ballistic missile attack on two Iraqi bases housing US soldiers, but both Ukrainian and Iranian officials say they suspected a mechanical issue brought down the Boeing 737-800 aircraft.

Global Affairs Canada did not immediately respond to a request for comment.

Airline officials said most of the passengers were en route to the Ukrainian capital, Kyiv, transiting through there to other destinations.

Ukraine’s President Volodymyr Zelenskiy extended his condolences to the families of the victims. His office said he had cut his visit to Oman short and was returning to Kyiv because of the crash.

“Our task is to establish the cause of the crash of the Boeing and provide all necessary help to the families of the victims,” said parliament speaker, Dmytro Razumkov, in a Facebook statement.

Ukraine International Airlines said it had indefinitely suspended flights to Tehran after the crash.

“It was one of the best planes we had, with an amazing, reliable crew,” Yevhen Dykhne, president of the Ukraine International Airlines, said at a briefing following the crash.

Zelenskiy, the Ukrainian president, ordered a sweeping inspection of all civil airplanes in the country, “no matter the conclusions about the crash in Iran.”

The plane had been delayed from taking off from Imam Khomeini International Airport by almost an hour. It took off to the west, but never made it above 2,400 metres in the air, data from the flight-tracking website FlightRadar24 indicates.

It remains unclear what happened. Qassem Biniaz, a spokesman for Iran’s Road and Transportation Ministry, said it appeared a fire struck one of its engines. The pilot of the aircraft then lost control of the plane, sending it crashing into the ground, Biniaz said, according to the state-run IRNA news agency.

Hassan Razaeifar, the head of air crash investigation committee, said it appeared the pilot couldn’t communicate with air-traffic controllers in Tehran in the last moments of the flight. He did not elaborate.

Ukrainian authorities have offered to help with the investigation of the plane crash.

“We’re preparing a group of specialists in order to help with the search operation and the investigation of the cause of the crash,”Honcharuk said.

The plane, fully loaded with fuel for its 2,300-kilometre flight, slammed into farmland near the town of Shahedshahr on the outskirts of Tehran. Videos taken immediately after the crash show blazes lighting up the darkened fields before dawn.

Resident Din Mohammad Qassemi said he had been watching the news about the Iranian ballistic missile attack on US forces in Iraq in revenge for the killing of Revolutionary Guard Gen. Qassem Soleimani when he heard the crash.

“I heard a massive explosion and all the houses started to shake. There was fire everywhere” he told The Associated Press. “At first I thought (the Americans) have hit here with missiles and went in the basement as a shelter. After a while, I went out and saw a plane has crashed over there. Body parts were lying around everywhere.”

AP journalists who reached the crash site saw a wide field of field of debris scattered across farmland, the dead laying among shattered pieces of the aircraft. Their possessions, a child’s cartoon-covered electric toothbrush, a stuffed animal, luggage and electronics, stretched everywhere.

Rescuers in masks shouted over the noise of hovering helicopters as they worked. They quickly realized there would be no survivors.

“The only thing that the pilot managed to do was steer the plane towards a soccer field near here instead of a residential area back there,” witness Aref Geravand said. “It crashed near the field and in a water canal.”

The Boeing 737-800 is a very common single-aisle, twin-engine jetliner used for short to medium-range flights. Thousands of the planes are used by airlines around the world.