OTTAWA (Reuters) - Canadian Prime Minister Justin Trudeau on Saturday said questions remain about Iran’s downing of a Ukrainian plane that killed all 176 aboard, including 57 Canadians, and that he expected full cooperation in the ongoing investigation.

Iran said earlier on Saturday that it shot down the plane in error.

“Canada and the world still have many questions, questions that must be answered,” Trudeau said in a news conference.

“It is absolutely necessary that Canada participate in this investigation. We expect the full cooperation of Iranian authorities,” he said.

Though Canada has not had diplomatic relations with Iran since 2012, Trudeau spoke to Iranian President Hassan Rouhani earlier in the day after Rouhani had said the military’s shooting down of the plane had been a “disastrous mistake”.

Rouhani committed to collaborating with Canadian investigators, working to de-escalate tensions in the region, and continuing a dialogue, Trudeau said.

Trudeau said a “full and complete” investigation is crucial in determining whether the downing of the airliner had indeed been a mistake, and he said compensation by Iran to the families should be “part of the mix”.

Trudeau said he told Rouhani that Iran’s admission that it unintentionally shot down the passenger jet was “an important step”, but he added that more steps must be taken to have “full clarity on how such a horrific tragedy could have occurred.”

Saying he was “furious” and “outraged”, Trudeau added: “Canada will not rest until we get the accountability, justice, and closure that the families deserve.”