The House ethics committee intensified its inquiry into allegations involving ex-Rep. Eric Massa (D-N.Y.) on Wednesday, announcing an investigative subcommittee and immediately interviewing at least one Democratic leader.

A Democratic source confirmed Wednesday that Majority Leader Steny Hoyer (D-Md.) participated in a “voluntary” interview before the subcommittee. The source said Hoyer was not subpoenaed to appear.

But it remained to be seen Wednesday night what other Members or aides — or potentially Massa himself — the subcommittee will invite, or potentially subpoena, for testimony and documents.

Prior investigative subcommittee queries suggest the panel could issue dozens of subpoenas, if it has not already done so.

A spokesman for the Committee on Standards of Official Conduct, commonly known as the ethics committee, declined to comment Wednesday.

In a statement announcing the investigative subcommittee, Chairwoman Zoe Lofgren (D-Calif.) and ranking member Jo Bonner (R-Ala.) said: “The allegations surrounding former Representative Massa are serious and warrant a full and complete investigation.”

The ethics committee opened an initial investigation tied to Massa in March, and unidentified aides in both Hoyer’s and Speaker Nancy Pelosi’s (D-Calif.) offices had been interviewed before Wednesday.

According to a copy of the resolution establishing the investigative subcommittee, the panel will examine whether Members, House officers or aides may have had “personal knowledge” or otherwise known of allegations that Massa created a “hostile work environment.” The inquiry will also examine whether Members or aides failed to report the accusations.

The New York lawmaker resigned from the House in March in the wake of allegations that he sexually harassed members of his staff.

Massa subsequently denied any wrongdoing during television and radio interviews but admitted to using “salty language” and engaging in improper physical contact with his staff.

It remains to be seen whether Massa will be subpoenaed in the investigation. Although he is no longer subject to the ethics committee’s jurisdiction, the panel could still compel him to appear for testimony or documents.

In its 2006 investigation of allegations tied to ex-Rep. Mark Foley (R-Fla.), who resigned from the House after reports emerged that he wrote sexually themed messages to a former House page, an ethics subcommittee did subpoena the former lawmaker although he was never deposed by the panel.

At the time, Foley’s attorney sought to defer the proceedings, citing ongoing criminal investigations. He also indicated the ex-lawmaker would plead the Fifth and refuse to testify if he were compelled to do so.

The subcommittee’s final report opted to not formally rule on whether Foley had violated House rules or other laws, noting that it did not have jurisdiction over him.

“The Investigative Subcommittee did not attempt to make formal findings regarding the conduct of former officials and employees because, as non-affiliates of the House, the Investigative Subcommittee lacks disciplinary authority over them,” the report stated. “The Investigative Subcommittee comments upon their conduct however, as set forth in this Report.”

Massa’s attorney did not return a telephone call Wednesday, nor did attorneys for former Massa Chief of Staff Joe Racalto or another Massa aide.

Both former Massa aides filed complaints with the Office of Compliance in late March over allegations of sexual harassment.

According to the reports of other recent investigative subcommittees, including the Foley probe, the panels have typically issued dozens of subpoenas for testimony or documents, suggesting the Massa inquiry could have similar results.

A spokesman for Pelosi said the Speaker has not yet interviewed with the ethics panel, but she has offered to do so.

“The Speaker has made herself available to meet with the ethics committee at their earliest convenience. Members of our staff have met with and fully cooperated with the ethics committee,” spokesman Nadeam Elshami said Wednesday.

Should the ethics subcommittee interview Pelosi, she would join the ranks of her predecessors in the Speaker’s office who have faced the ethics panel on a variety of matters, including ex-Reps. Dennis Hastert (R-Ill.), Newt Gingrich (R-Ga.), James Wright (D-Texas) and Tip O’Neill (D-Mass.).

House Republicans have repeatedly called for a review of what Democratic leaders knew about Massa’s behavior and how they responded.

A spokeswoman for the Majority Leader has previously acknowledged that the office was alerted to accusations against Massa by one of his aides in February, at which time Hoyer’s office threatened to report the matter to the ethics panel if Massa’s aides did not do so. Massa’s staff subsequently reported the allegations.