Iranian leaders said late Friday that their country's missiles unintentionally shot down a Ukrainian jet that crashed after taking off from Tehran this week after the U.S. and Canadian officials said intelligence showed that the Iranian military gunned down the plane.

A military statement carried by Iranian state media Saturday morning local time said the plane was mistaken for a “hostile target” after it turned toward a “sensitive military center” of the Revolutionary Guard. The military was at its “highest level of readiness,” it said, amid the heightened tensions with the United States.

All 176 people aboard Ukraine International Airlines Flight 752 on a Boeing 737 were killed in the crash early Wednesday, just after Iran fired ballistic missiles on Iraqi bases housing U.S. soldiers in retaliation for the U.S.' drone strike killing one of its top military leaders, Gen. Qasem Soleimani.

Among the dead on the flight were 63 Canadians, and Prime Minister Justin Trudeau said Thursday a missile was the cause of the plane crash.

Confirmation from US:Iranian missile likely caused Ukraine plane crash, Pompeo says

Iran's admission came after both the U.S. and Canada blamed the crash on a missile. Here's what we know now.

US, Canada says missile hit plane; Iran initially says 'no'

Before the admission late Friday, Ali Abedzadeh, head of Iran’s national aviation department, denied that any missile hit the passenger plane.

"What is obvious for us, and what we can say with certainty, is that no missile hit the plane," Abedzadeh said. "If they are really sure, they should come and show their findings to the world" in accordance with international standards.

Ali Rabiei, a spokesperson for the Iranian government, also accused the United States of spreading misinformation, CNN reported, citing Iranian state media.

"It is unfortunate that the psychological operation of the U.S. government, and those supporting it knowingly and unknowingly, are adding insult to the injury of the bereaved families and victimizing them for certain goals by propagating such fallacies," Rabiei said.

If Iran is found to have shot down the plane once the investigation is complete, the U.S. "and the world will take appropriate actions in response," Secretary of State Mike Pompeo said.

Treasury Secretary Steve Mnuchin said Friday his department would issue waivers for anyone who can help facilitate the investigation. Mnuchin also announced new sanctions on Iran, including sanctions on eight senior administration officials.

Will US aviation safety officials go to Iran to investigate the crash?

Recovering all the data from the Boeing 737's black box, the flight's data recorder, could take more than a month and the entire investigation more than a year, said Hassan Rezaeifar, who is in charge of the Iranian investigation team.

Ukraine has gained access to the "black box" from the plane, which records data from the flight and voices from the cockpit. In a WhatsApp message sent to USA TODAY, a spokeswoman for Ukraine's president, Iulia Mendel, wrote: "Yes, Ukraine has access to the black boxes."

Ukraine's foreign minister Vadym Prystaiko said Ukraine has not yet examined the data but that Iranian officials have been cooperative, CNN reported.

Two flight recorders were "damaged" but readable, and recovered from the crash, Abedzadeh said.

The U.S. National Transportation Safety Board said Thursday it received notification of the crash from Iran's aviation department and that it would "evaluate its level of participation."

NTSB added Friday: "The designation of an accredited representative is the first step toward that end. No decision has been made about travel and decisions are still being made about how the NTSB's involvement may unfold."

However, Hamid Baeidinejad, Iran's ambassador to the United Kingdom, on Friday appeared to indicate that American officials from the NTSB would travel to Iran to participate in the crash investigation.

It wasn't clear if the "accredited representative" would be an American government employee. There have been few, if any, U.S. government employees known to be traveling to Iran since the country's 1979 Islamic Revolution and the 444-day hostage crisis that ensued following the storming of the U.S. Embassy in Tehran.

What's happening at the site of the crash?

Baeidinejad, in London, denied a report that the site outside Tehran had "no security," "was not cordoned off" and that there was "no sign of any investigators."

CBS News' senior foreign correspondent Elizabeth Palmer tweeted that the crash site was not being protected early Friday for investigators and that local "scavengers (were) now picking the site clean."

Baeidinejad told USA TODAY that it wasn't true.

Contributing: Grace Hauck, Kim Hjelmgaard, Tom Vanden Brook, Chris Woodyard and John Bacon; The Associated Press