Eileen Murphy, a spokeswoman for The Times, declined to specify the reason that Mr. Jamieson had been investigated. In their message to Times employees, Mr. Baquet and Mr. Kahn said, “To protect the privacy of those involved, we do not intend to comment further.”

In his statement that was included as part of that note, Mr. Jamieson said, “Leading Metro for the last five years and working with the incredible Times team has been the high point of my professional life.” After issuing his apology, he added: “I’m especially proud of all the talent I’ve helped bring to The Times. Susan Chira is a wonderful editor, a true New Yorker, and I know Metro will rise to even greater heights under her leadership.”

Mr. Jamieson declined to comment beyond that statement. His Twitter profile appeared to have been removed as of Monday afternoon.

Ms. Chira was part of a team that won a Pulitzer Prize this year for coverage of workplace sexual harassment issues. She has previously served as The Times’s deputy executive editor, foreign editor and Tokyo correspondent, and as a reporter on the national, business and metro desks.

Last year, The Times investigated another newsroom employee, the prominent political reporter Glenn Thrush, after learning about allegations of inappropriate behavior against him that were later the subject of a report by the website Vox. After a monthlong investigation, Mr. Thrush was suspended without pay. He returned to the newspaper in late January but was moved from the team covering the White House to a beat focused on the country’s social safety net.