The Senate is taking the "unprecedented step" of bringing on an independent investigator to examine allegations that Senate President Stanley Rosenberg's husband Bryon Hefner groped three men and kissed another against his will in social settings related to their work on Beacon Hill.

In an announcement late Thursday night, several hours after a Boston Globe story outlined the alleged incidents, Senate Majority Leader Harriette Chandler of Worcester said Rosenberg would recuse himself from the investigation and remain as Senate president, with all the responsibilities of the office, while the probe unfolds.

It's unclear how long the investigation will take or who will conduct it.

"These charges are very serious and very disturbing, and I am shocked and saddened," Chandler said. "In order to ensure a completely impartial process, and because of these unique circumstances which involve the Office of the Senate President, we will be going to the unprecedented step of bringing in an independent special investigator."

Chandler added, "I appreciate that President Rosenberg has recused himself from playing any role in this investigation. While the Senate President will be recused in this matter, he will remain in the Office of the Senate President and retain his responsibilities for all other matters before the Senate. I look forward to working with the Minority Leader in the true spirit of bipartisanship to resolve this issue in a transparent and expeditious manner."

Earlier Thursday evening, Rosenberg supported the call for an independent investigation of the allegations "regarding the activities of my husband and their effects on Senate business" and said he would leave it to Chandler and Senate Minority Leader Bruce Tarr to develop a structure and process for the probe.

Gov. Charlie Baker and Attorney General Maura Healey reacted to the Globe report on Thursday in part by saying an investigation is needed.

"Frankly, I'm appalled by the allegations. They're disturbing, they're distressing, and I really felt for the people, when I read the story, who came forward. And I think it's really important for the Senate, as soon as possible, to conduct a thorough investigation of the allegations," Baker said.

The men who claimed they were groped and subjected to unwanted sexual advances by Hefner include a Beacon Hill aide, a lobbyist, a public policy advocate and a man who worked on Beacon Hill when Hefner allegedly put his hand up his shorts at a fundraiser, according to the Globe article.

Rosenberg, an Amherst Democrat who said this week he plans to seek re-election next year, was not in the State House when the story was first posted online.

In an afternoon statement, he said, "This is the first I have heard about these claims. Even though, based on what little I have been told, these allegations do not involve members or employees of the Senate and did not occur in the State House, I take them seriously. To the best of my recollection I was not approached by anyone with complaints during or after the alleged incidents made in this article or I would have tried to intervene."

Hefner issued a statement Thursday through his attorney, saying he was "shocked to learn of these anonymous and hurtful allegations" outlined in the article, which was written by Globe columnist and former State House reporter Yvonne Abraham.

"To my knowledge, no one has complained to me or any political or governmental authority about these allegations which are now surfacing years afterward. As one can imagine, it is incredibly difficult to respond to allegations by unnamed and unidentified individuals that involve an extended period of time, particularly in the current environment," the statement in the Globe said, without identifying the attorney.

The investigation will come midway through the 2017-2018 session, with lawmakers advancing major health care and criminal justice bills and preparing for a new annual budget cycle, which gets underway with a public hearing next week on revenue expectations.