FBI Director James Comey seemed to suggest Thursday that Attorney General Jeff Sessions had an undisclosed Russia problem.

Comey said the FBI became "aware of facts that I can't discuss in an open setting, that would make (Sessions') continued engagement in a Russia-related investigation problematic."

That statement drew a lot of attention. But it may amount to less than meets the eye.

Speaking to senators later in closed session, Comey confirmed that he had been talking about a story that NBC News and other outlets had already reported — about classified intelligence suggesting an undisclosed meeting between Sessions and the Russian ambassador to the U.S. in April 2016 at the Mayflower Hotel in Washington. That's according to two sources familiar with what Comey said.

Related: Did Trump, Kushner Sessions Have an Undisclosed Meeting With Russians?

"Jeff could add a lot of light to it as to why he recused himself," Sen. Joe Manchin, D-W.V., a member of the Senate Intelligence Committee, told NBC News. "There's one meeting we don't (have details about) and people would like to know about it."

But Sessions' spokeswoman, Sarah Isgur Flores, has denied that any such meeting happened. A source close to Sessions says he will deny it, as well, if asked Tuesday when he appears before the Senate Appropriations Committee.

NBC News reported June 1 that the FBI and Congress have been examining the Mayflower event. Five current and former U.S. officials said they are aware of classified intelligence suggesting there was some sort of private encounter between Trump and his aides and the Russian envoy.

That would be a huge problem for Sessions, who has already come under fire for failing to disclose two separate contacts with Russian ambassador Sergey Kislyak. Jared Kushner, the president's son-in-law, also denied through a spokesman that he met privately with Kislyak that day.

However, the officials acknowledged to NBC News that the evidence does not amount to proof, and they have declined to provide details about it. Comey, speaking to senators in Thursday's closed session, also acknowledged that the FBI did not have proof the meeting occurred, a source familiar with the matter said.

"The then-Senator did not have any private or side conversations with any Russian officials at the Mayflower Hotel," Flores said in a statement.

A U.S. official with knowledge of the matter told NBC News that the FBI also is scrutinizing the Mayflower event, which was sponsored by a think tank that has been characterized as pro-Russian. The official said the FBI is interested in who was at the event and what was said, in the context of the counter-intelligence investigation into Russian election meddling. That official said there was no indication the bureau is zeroing in on Sessions.

It has long been known that Trump briefly met Ambassador Kislyak that day at a VIP reception shortly before he gave a foreign policy address at the hotel. But witnesses said it wasn't a private meeting, and White House officials dismissed it as inconsequential.

"Mr. Trump warmly greeted Mr. Kislyak and three other foreign ambassadors who came to the reception," the Wall Street Journal reported in May 2016.

Kushner and Sessions were also in the room, contemporaneous news reports say. Sessions' aides have insisted he did not speak to Kislyak.

In March, the Center for the National Interest, the right-leaning, Russia-linked group that hosted the event, said that the receiving line "moved quickly and any conversations with Mr. Trump in that setting were inherently brief and could not be private. Our recollection is that the interaction between Mr. Trump and Ambassador Kislyak was limited to the polite exchange of pleasantries appropriate on such occasions."

Sessions recused himself from the Russia investigation after it emerged that he had met twice with Kislyak after telling senators under oath during his confirmation hearing that he had not met with Russian officials about the Trump campaign.

"In retrospect," Sessions told reporters, "I should have slowed down and said, 'But I did meet one Russian official a couple of times, and that would be the ambassador.'"

Sessions said he had not disclosed the meetings because they were in his capacity as senator, not Trump campaign surrogate.

Related: Comey Told Senate About Potential Third Meeting Between Sessions, Russians

In a March congressional hearing on the Russia investigation, Rep. Mike Quigley, a Chicago Democrat on the House Intelligence Committee, accused Sessions of having committed perjury about an alleged undisclosed third meeting in April.

He noted that Sessions had failed to disclose meetings with Kislyak in July and September, during a time the Russians were "hacking and dumping" stolen emails in the election campaign.

Then-Republican presidential candidate Donald Trump gives a thumbs up after a foreign policy speech at the Mayflower Hotel in Washington on April 27, 2016. Evan Vucci / AP

He added, "Unfortunately, what we're reading now is that there was a third meeting as early as April of last year in Washington, D.C., a meeting at which candidate Trump was present and the Russian ambassador was present. At some point in time, this goes well beyond an innocent, under the best of circumstances, 'Oh I forgot' sort of thing, or 'That doesn't count.' When you correct your testimony in front of the United States Senate, you're still under oath and you're swearing to the American people that what you're saying is true. Well, the third time is well beyond that and is quite simply, perjury."

Sen. Al Franken, D.-Minn., in a March letter to the FBI with Judiciary Committee Democrat Patrick Leahy of Vermont, asked the FBI to investigate any contacts between Sessions and Russian officials, and to brief him on the results.