Ms. Turness said that she and Mr. Williams had spoken with the “Nightly News” team on Thursday and addressed more employees in an editorial meeting on Friday.

“Brian apologized once again, and specifically expressed how sorry he is for the impact this has had on all of you and on this proud organization,” Ms. Turness said in the memo, which was obtained by The New York Times.

NBC News executives have not publicly addressed the issue, hunkering down on Friday as Mr. Williams’s troubles continued to draw a frenzy of criticism. Across the web, commentators have been aggressive in questioning not only Mr. Williams’s reporting but NBC’s handling of the problem. Some military veterans and commentators have called for his resignation.

Executives canceled external meetings and said that the issue was absorbing all of their focus, people in the news division said. Current and former NBC employees discussed the ultimate fate of the news anchor, shocked by his fall from grace and the turmoil it had created at the network.

Mr. Williams has not addressed the issue publicly since Wednesday, when he apologized on his newscast for embellishing an account of an incident in 2003; over the years he came to say that he was in a helicopter that was hit by enemy fire, an assertion he now says is not true. On his newscasts Thursday and Friday, he did not mention the controversy.