WASHINGTON (Reuters) - A three-year U.S. House probe into allegations of ethical lapses including sexual misconduct and illicit drug use by Republican Representative Matt Gaetz will expand to investigate whether he tried to obstruct the inquiry, the committee leading it said on Tuesday.

The House of Representatives Ethics Committee said in a statement, "During the course of its investigation, the committee has also identified additional allegations that merit review." The panel noted "difficulty" in obtaining information from the congressman.

The committee, which has been investigating Gaetz since April 2021, said it was ending its investigation of some of the allegations against Gaetz, including claims that he had misused campaign funds and state IDs.

Gaetz, 40, is a four-term northwest Florida congressman and close ally of Republican presidential candidate Donald Trump who played a central role in the 2023 toppling of House Speaker Kevin McCarthy. He has repeatedly denied all allegations of wrongdoing.

"The Ethics Committee is now opening new frivolous investigations," Gaetz said in a statement on X, as he blamed McCarthy, who no longer is a member of Congress, for seeking revenge. "Kevin McCarthy showed them the man, and they are now trying to find the crime."

The committee said it was continuing its probe into Gaetz's behavior, having spoken with more than one dozen witnesses and issued 25 subpoenas while reviewing "thousands of pages of documents."

Besides allegations of sexual misconduct and illicit drug use, the panel also is continuing to look into whether he accepted improper gifts and dispensed special privileges and favors to individuals with whom he had a personal relationship, the committee said.

"There has been a significant and unusual amount of public reporting on the Committee's activities this Congress. Much of that reporting has been inaccurate," the committee said in its statement.

The panel is also looking into Democratic Representative Henry Cuellar of Texas, after he and his wife were indicted in a bribery case.

Last year, Republican then-Representative George Santos was expelled from Congress after the House Ethics Committee unanimously found that he had filed false or incomplete campaign finance reports, used campaign funds for personal purposes and engaged in fraudulent conduct.

(Reporting by Richard Cowan; Editing by Scott Malone and Deepa Babington)