Washington CNN  — 

Sen. Susan Collins sent a written note early Wednesday morning during President Donald Trump’s impeachment trial minutes before Chief Justice John Roberts admonished both legal teams, a source with knowledge of the event tells CNN.

It is unclear if the note from Collins, a Maine Republican, led directly to Roberts’ comments, or had specific language for him, but the note came shortly before the chief justice spoke. The note was sent as House Judiciary Chairman Jerry Nadler, a Democrat from New York, spoke and appeared to accuse senators of a “cover-up.”

Senate Parliamentarian Elizabeth MacDonough was seen on TV cameras speaking to Roberts at 12:48 a.m. ET. It is not clear what the conversation between the two was about, but Roberts addressed the Senate at 12:55 a.m.

There were also heated language from one of the President’s attorneys, Pat Cipollone, in the preceding 30 minutes, and Roberts specifically addressed both legal teams in his remarks.

Sen. Susan Collins of Maine, at right, walks with Sen. Dan Sullivan of Alaska to the Senate chamber at the Capitol on Wednesday.

“I think it is appropriate at this point for me to admonish both the House managers and the President’s counsel, in equal terms, to remember that they are addressing the world’s greatest deliberative body,” Roberts said, appearing to refer to notes on the dais.

The Supreme Court’s public information officer did not comment.

Collins was reluctant to acknowledge any contribution to the remarkable rebuke of the parties arguing the impeachment trial. When she came off the floor about 2 a.m. ET Wednesday, a reporter told her that she was seen handing a note up to the dais, to the parliamentarian, she replied coyly: “Who me? I did that?”

Collins is a moderate senator up for reelection this year and her actions have been closely watched during the trial, especially for any indication she may break from Trump or the Senate GOP leadership and support a call for witnesses.

The full moment of Collins writing or handing a note, or it being handed up to MacDonough, does not appear to have been broadcast. The Senate controls the one TV feed distributed from the chamber, and the camera has been zoomed in on the House manager or lawyer for the President while that person is speaking at the lectern. The moment between MacDonough and Roberts can be seen on TV because Nadler had wrapped up speaking, and the camera zoomed out to a broader view.

At one point during the debate, Nadler accused Republican senators of “voting for a cover-up.”

“So far, I’m sad to say, I see a lot of senators voting for a cover up. Voting to deny witnesses, an absolutely indefensible vote, obviously a treacherous vote,” Nadler said. “A vote against an honest consideration of the evidence against the President. A vote against an honest trial. A vote against the United States.”

Republican Sen. Ron Johnson of Wisconsin said of the chief justice’s comments: “I think we all realize he was admonishing the House Democrats, but, again, trying to keep it nonpartisan.

“You don’t come into the Senate and accuse senators of engaging in a cover-up or saying that we’re on trial. No, we’re not,” the Wisconsin Republican said, calling the comments “jaw-dropping, couldn’t really believe what we were hearing.”

Illinois Democratic Sen. Dick Durbin said he was “glad that the chief justice admonished both sides to remember where they are.”

“I could understand how people on the other side could take offense, but there were some things said as well by the President’s counsel,” Durbin said, but added, “It’s behind us. We’ve got a bigger job to focus on.”

During his remarks, the chief justice recalled the impeachment trial of Judge Charles Swayne and a debate over the word “pettifogging.”

“In the 1905 Swayne trial, a senator objected when one of the managers used the word ‘pettifogging’ and the presiding officer said the word ought not to have been used,” Roberts said. “I don’t think we need to aspire to that high of a standard, but I do think those addressing the Senate should remember where they are.”

CNN’s Clare Foran, Ali Zaslav and Ariane de Vogue contributed to this report.