Trudeau said he knows the news will come as a shock to grieving families.

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The crash killed all on board, including 138 people who were headed to Canada.

Ukrainian officials have said a missile is on their list of potential causes for the crash.

The plane crashed minutes after taking off from Tehran’s airport on Wednesday.

Trudeau repeatedly said there needs to be a complete and thorough investigation to get “a complete picture of what happened.”

Trudeau said it was too soon to blame the United States, which triggered a chain of events that led to the crash with its killing of a top Iranian general last week. He said there needs to be further investigation.

The crash came after a week of soaring tensions in the Middle East, occurring just hours after Iran launched missile attacks on bases in Iraq where American and allied troops are stationed. Iran said the attacks were retaliation for the American killing of Maj.-Gen. Qassem Suleimani near Baghdad.

Earlier Thursday, U.S. President Donald Trump suggested he believes Iran was responsible, without laying direct blame.

“Somebody could have made a mistake on the other side,” Trump said in a Washington news conference, noting the plane was flying in a “pretty rough neighbourhood.”

“Some people say it was mechanical,” Trump added. “I personally don’t think that’s even a question.”

Trudeau said he had no comment on what Trump had said.

Iran’s civil aviation authority is leading the investigation, under international rules for probes of such crashes. The organization said Thursday it had invited Canadian investigators from the Transportation Safety Board to join a growing team probing the crash.

Trudeau said Canadian consular officials are headed to Turkey and that Iran would be open to issuing visas so they could be granted access to the country. He said Iran has indicated “an openness” to Canada taking part in an investigation. Canada and Iran broke off diplomatic relations in 2012.

This report by The Canadian Press was first published Jan. 9, 2020.