WASHINGTON — Special counsel Robert Mueller's investigators have interviewed Attorney General Jeff Sessions and former FBI Director James Comey as part of the ongoing federal probe into Russian meddling in the 2016 election, according to two people familiar with the investigation.

Sessions was interviewed "for hours" last week, a Justice Department spokeswoman said, marking the first known time a member of President Donald Trump's Cabinet has been interviewed. A Justice Department official said Sessions was accompanied by his lawyer Chuck Cooper.

Asked Tuesday afternoon in the Oval Office if he had talked to Sessions about what the attorney general might have said to the investigators, Trump said he hadn't. "No, I didn't," said the president, "but I'm not at all concerned."

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Comey was interviewed late last year, according to a source close to the former FBI director. Comey was fired by Trump in May and later testified that he had refused urgings by Trump to promise his loyalty and drop his investigation into former national security adviser Michael Flynn.

The focus of Comey’s interview was the memos he wrote after his private meetings with the president, the source said, which is at the heart of Mueller’s probe into whether Trump has obstructed the investigation.

Sessions' rank within the administration along with Comey’s close proximity to the obstruction angle may indicate that Mueller is zeroing in on central characters as he enters the more advanced stages of the investigation.

Trump has repeatedly said there was no collusion between his campaign and the Russian government in the 2016 election, and his lawyers have predicted that the federal probe will soon conclude, leaving the president free of any charges of wrongdoing.

"Out of respect for the special counsel and his process," said White House attorney Ty Cobb about reports of Sessions being interviewed, "and because of the privacy obligations we owe to potential or actual witnesses, the White House does not comment on witness appearances before the special counsel."

The New York Times was the first to report on the interviews that Mueller's team conducted with Sessions and Comey. It is unknown what Sessions was asked or how he responded.

The roles Sessions has played within the Trump campaign and the administration make him of prime interest to Mueller, who is probing not just possible collusion but also efforts by the president to obstruct the investigation. As a senior member of the Trump campaign, Sessions met with Russian ambassador Sergey Kislyak and sat in on a meeting where George Papadopoulos presented a plan to set up high-level talks with Russia.

Comey, left, walks with Mueller to a ceremony announcing Comey's nomination to become FBI director at the White House in June, 2013. Win McNamee / Getty Images file

Papadopoulos, a previously little-known figure in the Trump campaign, pleaded guilty to lying to the FBI in October. Testifying before Congress in November, Sessions said he did not initially recall the meeting with Papadopoulos until media reports jogged his memory. He said he pushed back on the idea of setting up a meeting between then-candidate Trump and Russian President Vladimir Putin.

Although the U.S. attorney general would usually have jurisdiction over a federal probe, Sessions recused himself from the Russia investigation in March after media reports emerged about his meetings with Kislyak. That recusal put Deputy Attorney General Rod Rosenstein in charge, who later appointed Mueller as special counsel. That chain of events has strained the relationship between Sessions and Trump, with the president blaming his attorney general for Mueller's appointment in private and lashing out on him via Twitter.

Despite the criticism, Sessions has remained loyal to Trump.