Prime minister Justin Trudeau calls deadly plane shooting a 'national tragedy,' Canadian crash team en route to Iran to investigate

Fifty-seven Canadians died when Iran's military shot down the Boeing 737.

Prime Minister Justin Trudeau said a crash team was en route to Iran to participate in the investigation of the plane crash that killed 176 people, including 57 Canadians.

Iran has admitted that it unintentionally shot down the plane, which was was mistaken for a "hostile flight" after it turned toward a "sensitive military center." The plane was "unintentionally hit" with an anti-aircraft missile, according to an official Iranian statement released early Saturday morning local time.

Trudeau asked Iranian President Hassan Rouhani that Canada be included fully in the investigation -- from the black box to DNA identification, and that consular access be provided

"Earlier this morning I spoke with Iranian president Rouhani," Trudeau said in a press conference Saturday. He called Iran’s admission of "unintentionally" shooting down the plane "a very important first step” toward providing answers for the crash victims' families, though he also said there are still many questions "that must be answered."

"A full and complete investigation must be conducted," Trudeau said. "We expect the full cooperation of Iranians," he added.

Trudeau said the team would also support the families of the Canadian victims. Three visas have been approved to send lead members from a Canadian crash team -- the country's version of the U.S.' National Transportation Safety Board -- to Tehran. The team is expected to arrive at 4 p.m. Saturday local time.

Rouhani, meanwhile, expressed his regret in a post to Twitter.

"Armed Forces’ internal investigation has concluded that regrettably missiles fired due to human error caused the horrific crash of the Ukrainian plane & death of 176 innocent people," Rouhani said, writing in English. "Investigations continue to identify & prosecute this great tragedy & unforgivable mistake."

"The Islamic Republic of Iran deeply regrets this disastrous mistake. My thoughts and prayers go to all the mourning families. I offer my sincerest condolences," he added.

ABC News' Joshua Hoyos, Marc Nathanson and Justin Doom contributed to this report.