Details of what the Justice Department has now provided to Mueller’s team, which sources say has been investigating whether President Donald Trump sought to obstruct a federal inquiry into possible connections between his presidential campaign and Russian operatives, reflect how widely investigators are casting their net.
In an Oval Office meeting after Mueller's appointment, Trump told Sessions he should resign, prompting the attorney general to submit a letter of resignation, according to The New York Times. But Trump ultimately rejected the resignation after advisers warned against it in the wake of Comey’s firing.
A month after that episode, Trump wanted to have White House aides fire Mueller but backed off after White House counsel Don McGahn and others made clear they were opposed to such a move, a source familiar with the deliberations told ABC News.
Emails and other documents produced within the Justice Department during that time, including emails with White House officials, have now been sent to Mueller’s office, according to a source with knowledge of the matter.
The special counsel has already secured charges against four Trump associates, including Flynn.
Referring to the Justice Department, Yates told lawmakers last year, "We believed Gen. Flynn was compromised in regards to the Russians" and “could be blackmailed by the Russians."
The Justice Department has now provided Mueller’s team with internal documents related to the matter, according to the source with knowledge of the matter.
Mueller’s team also asked former senior Justice Department officials for information from their time at the department, sources familiar with the request previously told ABC News.
Meanwhile, Sessions has faced public criticism from Trump over his recusal and Rosenstein's subsequent appointment of Mueller.
At one point last year, Trump told reporters he wouldn't have nominated Sessions to run the Justice Department had he known Sessions would give up oversight of the investigation.
In announcing his recusal, Sessions said he and "senior career department officials" spent "several weeks" discussing whether his role as top foreign policy adviser to Trump's presidential campaign last year meant his "impartiality might reasonably be questioned."
Such internal discussions have been turned over to Mueller’s team, the source familiar with the matter told ABC News.
Sessions was interviewed by Mueller's team two weeks ago. Rosenstein was interviewed last summer.
In the wake of Flynn's guilty plea, the former national security adviser is now cooperating with Mueller’s investigation, which has already netted another guilty plea and an indictment against two Trump associates.
Former Trump campaign adviser George Papadopoulos has pleaded guilty to lying to the FBI about his time with the campaign. In court documents, he said he told Sessions and Trump during a 2016 meeting that he was working with Russians to orchestrate a meeting between Trump and Russian President Vladimir Putin. Sessions rejected the suggestion that Papadopoulos should help orchestrate a meeting between the two.
In addition, former Trump campaign manager Paul Manafort and his former business partner Rick Gates have been indicted on money-laundering and other charges tied to their previous lobbying efforts. They have pleaded not guilty.