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.
The Times previously reported that a young foreign policy aide on the Trump campaign, George Papadopoulos, revealed he knew of hacked Democratic Party emails to Australian Ambassador Alexander Downer over late-night drinks in London.