President Donald Trump and his allies have long insisted that what he calls the “fake dirty dossier” was wholly “responsible for starting the totally and discredited witch hunt” by special counsel Robert Mueller.

But, beginning in July 2016, that so-called “dossier” actually sat for several weeks inside an organized crime unit at the FBI’s New York field office, even as counterintelligence agents in Washington, D.C. – unaware of the new allegations – were already investigating Russian efforts to hijack American democracy…

The following account, relayed to ABC News by several sources familiar with the federal probe, reflects how the FBI’s investigation into contacts between Russian operatives and Trump’s campaign team, including Page, was well underway in the summer of 2016 by the time a former British spy handed the FBI a packet of startling and salacious allegations tied to Trump.