The FBI investigation into the Trump campaign's ties to Russia was originally known as "Crossfire Hurricane" before it was widely known to the public and even the bureau itself, officials told The New York Times.

The case, named after a Rolling Stones lyric, was used by only the small group of agents sent to interview the Australian ambassador to the United Kingdom, who had evidence of possible collusion between Russia and a Trump adviser.

Five agents embarked to London in the summer of 2016 for a rare interview with the diplomat after deliberations between American and Australian officials, where they gathered information that would provide the basis for the Russia probe that is still ongoing.

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The Times previously reported that a young foreign policy aide on the Trump campaign, George PapadopoulosGeorge Demetrios PapadopoulosTale of two FBI cases: Clinton got warned, Trump got investigated Trump says he would consider pardons for those implicated in Mueller investigation New FBI document confirms the Trump campaign was investigated without justification MORE, revealed he knew of hacked Democratic Party emails to Australian Ambassador Alexander Downer over late-night drinks in London.

Downer reportedly notified U.S. intelligence officials of his run-in with Papadopoulos after the emails, which contained damaging information about 2016 Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE just as the aide had said, began to leak to the public.

From there, the tight group of FBI agents went forward in interviewing Trump associates, which was kept secret for fear of leaks that could sway the campaign.

The official look into the Trump campaign reportedly began just days after the bureau closed its investigation into Clinton for her use of a private email server while serving as secretary of State.