Canada’s rescue of several Americans from the 1979 Iran hostage crisis was always thought to have been carried out in complete secrecy.

But an investigation by CBC’s French service, Radio-Canada, reveals several senior Iranian officials were aware of the six Americans hiding out at the Canadian Embassy during the 444-day-long hostage crisis.

Timeline of Iran hostage situation: Jan. 1979: Iranian Shah Mohammed Reza Pahlavi deposed.

Shah diagnosed with cancer and allowed into U.S. for treatment.

Nov. 1979: 600 students, under the name Muslim Students of the Imam Khomeini Line, launch protest at American Embassy in Tehran.

Students take more than 70 Americans hostage and demand that the deposed shah be returned to the Iranian government to face justice.

Amid chaos six U.S. Embassy staff (four men, two women) escape to Canadian Embassy, where they are sheltered for 3 months

The Canadian Caper: Hidden Americans are disguised as filmmakers and smuggled aboard a plane to Frankfurt, Germany.

Hostage situation ends after 444 days.

An interview with a former high-ranking Iranian official reveals that some people within the Iranian government knew more than they let on.

But those Iranian allies, who opposed the hostage-taking, kept quiet because they knew that speaking out would mean risking their own lives at the hands of radical groups.

Students take Americans hostage

The hostage situation that unfolded in November 1979 began when about 600 student protesters took the U.S. Embassy in Tehran by storm. The protesters were angry with the U.S. for allowing Mohammed Reza Pahlavi, the deposed shah, into the United States for cancer treatments.

The frustrated students took more than 70 U.S. Embassy staff hostage, and demanded that the Pahlavi be returned to the Iranian government to face justice.

During the chaos, six Americans — four men and two women — fled to the Canadian Embassy and hid there for three months as the crisis unfolded. Those Americans eventually escaped in an operation dubbed the "Canadian Caper," and popularized by the film Argo.

In true made-for-Hollywood fashion, the Americans were smuggled aboard a plane disguised as a film crew and flown to Frankfurt, Germany.

When the story broke in Canada, the minister for External Affairs, Flora MacDonald, said they were able to evade detection because of the tumultuous scene in Iran.

Ahmad Salamatian, who was an official with the Iranian government during the hostage crisis, says speaking up would have meant risking his life. (CBC)

"The country was preoccupied with its own internal elections — there were many things going on in Tehran — and we were therefore able to move with less notice than we might have otherwise," MacDonald said.

But they might not have been as discreet as she imagined.

Iranian officials knew, but did nothing

Ahmad Salamatian, vice-minister of Foreign Affairs during the hostage crisis, says he knew about the Americans but kept it to himself.

"It was absolutely certain that the people in charge at Iran's foreign affairs ministry, particularly the protocol department, knew there were diplomats in the Canadian Embassy," he said.

Salamatian, who was responsible for negotiating with the United Nations, says there were several officials who, like him, knew the secret but kept it quiet. They knew they would be risking their lives if they spoke in favour of freeing the hostages.

U.S. diplomat Bruce Laingen was one of three Americans held hostage at the Iranian Foreign Affairs Ministry during the crisis.

He says he even told an Iranian official about the six missing Americans, hoping they would be able to help them escape.

In an interview with Georgetown University, Laingen said that while the officials couldn’t help, they never revealed what they knew.

"They never divulged the fact that they were there. They knew it, but kept it secret and I give them credit for that, " he said.

Dr. James Devine, assistant professor in politics and international relations at Mount Allison University in Sackville, N.B., says he isn’t surprised some Iranian diplomats were in the know.

"I think in 1979, the perception of Iran in the West was of a very homogenous, very radicalized, very aggressive country where everybody hated Westerners," he said.

But, he added, not everyone in the country was on the same page.

"The idea that the negotiators and the Americans would be talking about this frankly is not that surprising," Devine said. "The problem wasn’t the negotiators and the official government, it was [Ayatollah Khomeini] and the radical groups."

Even Ken Taylor, the Canadian ambassador seen by many as a hero for his role in the escape, says he was aware the Iranians knew something.

"I think there was some suspicion among Iranians that some U.S. diplomats were out of the embassy," he said. "I don't think they took it seriously enough to pursue it, and certainly it didn't govern our thinking."