WASHINGTON — A Senate investigation into Russia's meddling in the 2016 presidential election has revealed a possible obstruction of justice case against President Donald Trump, Democratic Sen. Dianne Feinstein said on "Meet The Press" Sunday.

"The [Senate] Judiciary Committee has an investigation going as well and it involves obstruction of justice and I think what we're beginning to see is the putting together of a case of obstruction of justice,” Feinstein, the panel's top Democrat, said.

“I think we see this in the indictments, the four indictments, and pleas that have just taken place and some of the comments that are being made," Feinstein added, referencing the indictments of former Trump campaign chairman Paul Manafort and his associate Rick Gates, who face charges that include conspiracy and money laundering that were uncovered during Special Counsel Bob Mueller's investigation into potential links between Trump and Russia. Also charged in connection to the Mueller investigation are Trump's former National Security Adviser Michael Flynn and former campaign adviser George Papadopoulos, who both pleaded guilty to lying to the FBI.

"I see it in the hyper-frenetic attitude of the White House, the comments every day, the continual tweets. And I see it most importantly in what happened with the firing of Director [James] Comey, and it is my belief that that is directly because he did not agree to ‘lift the cloud’ of the Russia investigation. That’s obstruction of justice,” Feinstein said.

Trump fired former FBI Director James Comey earlier this year in the midst of the bureau's investigation into Russia's interference into the 2016 presidential election.

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The Senate Judiciary Committee is conducting just one of a number of congressional investigations that touch the fallout from Russia’s alleged election interference, including active probes in both the Senate and House Intelligence Committees. The Judiciary Committee’s purview has focused on oversight of the Justice Department and the FBI.

Feinstein, who is also a member of the Senate's Intelligence Committee, said that she does not believe Flynn acted as a "rogue agent" in his conversations during the transition with Russian Ambassador Sergey Kislyak, communication that was the subject of Flynn's guilty plea in federal court on Friday for making false statements to the FBI.

Court documents showed that Flynn was urged by two transition officials to contact Russians, and sources have told NBC News that those officials are Trump’s son-in-law and senior adviser Jared Kushner, and K.T. McFarland, who later served as deputy national security adviser in the White House.

Sen. Susan Collins, R-Maine, who is also a member of the Senate’s Intelligence Committee, said in an interview Sunday it’s still unclear whether or not there was any form of collusion between Russians and people in Trump’s orbit.

The conversations between Flynn and Kislyak during the transition “should not have been taking place,” Collins said, since there was only one president at the time, President Obama. “But that does not confirm collusion."

Collins added that she would still like to hear from Flynn because she believes “he could contribute a great deal to our investigation,” but Flynn has declined their invitations, citing the Fifth Amendment. Collins said their committee does not have access to the interview transcripts in Mueller’s probe.

The New York Times also reported this week that Trump has pressed top Republicans, including the chairman of the Senate Intelligence Committee, to end their inquiries into Russia. Collins on Sunday noted that the president has never contacted her specifically about it, but criticized any meddling by the president into the ongoing investigations.

“Even if it’s inexperience, that doesn’t make it right," she said. “The president should have no comment whatsoever on either of these investigations. The only thing he should be doing is directing all of his staff and his associates to fully cooperate.”

Feinstein on Sunday also noted that her concern about the White House “rises with the day.”

Asked specifically whether her concern with President Trump’s ability to do the job rises by the day, she responded, “oh yes,” and added that a moment came a month ago where she felt enough is enough.

But Feinstein did not go as far as saying there’s a need to remove Trump from office yet.

“I believe it’s time for us to finish our investigation and I don’t want to bias any part of the investigation with premature thinking,” she said. “I think that’s very important.”