Watch: 'We're going to find out who knew what and when' Graham says at Crossfire Hurricane hearing

Former acting Attorney General Sally Yates told a Senate committee on Wednesday that the FBI acted without her authorization when interviewing incoming national security advisor Michael Flynn in January 2017.

Yates testified before the Senate Judiciary Committee during its "Oversight of the Crossfire Hurricane Investigation" hearing, part of the committee's large effort to learn more about the Obama administration's efforts to investigate the 2016 Trump campaign for possible collusion with Russia. 

Yates faced repeated questions about the approval of FISA court warrants, based on the now-discredited Steele Dossier, to conduct surveillance on campaign members. 

Carolina GOP Sen. Lindsey Graham, the committee chairman, concluded the the hearing by suggesting no high ranking official at the FBI understood that the dossier contained deeply flawed information. 

"I find it hard to believe that the dossier was used four times to get a warrant against (Trump adviser) Carter Page and nobody knew it was a bunch of garbage," he said. "I want to make sure this never happens again.

Graham also argue that he found it "impossible to believe" that Yates, former FBI Director James Comey and others were not aware that the sub source of the dossier disavowed the report. 

Graham said that the committee's ongoing priorities will be to speak with the intel analyst and the case agent at the FBI who vetted the dossier, specifically in an attempt to construct a comprehensive timeline of when the pertinent intelligence personnel came to understand that dossier was comprised of unreliable information.  

"We're going to find out who knew what and when, and if they knew the dossier wasn't reliable and they continued to use it, they're going to be in serious trouble with the law," he said

When asked whether Comey “went rogue,” when he sent agents to the White House to interview General Michael Flynn, Yates replied, "You could use that term, yes."