WASHINGTON — The normally secretive House Ethics Committee made a rare public pronouncement on Thursday, announcing it has launched a high-profile investigation into allegations that the House intelligence committee chairman may have improperly disclosed classified information while leading a probe of Russian interference in the 2016 presidential election.

The inquiry into Rep. Devin Nunes, R-Calif., marks the first time in more than two decades that the ethics panel has publicly acknowledged investigating possible misuse of classified information by a House member.

Nunes said Thursday he is stepping aside from leading the inquiry, citing the ethics review. Nunes called the charges false and politically motivated, but said it was in the best interest of the intelligence panel to have Rep. Michael Conaway, R-Texas, temporarily take charge of the Russia probe.

The ethics investigation will be led by Chairwoman Susan Brooks, R-Ind., and Rep. Ted Deutch, D-Fla., the panel's ranking member.

Two watchdog groups, Democracy 21 and Citizens for Responsibility and Ethics in Washington, had requested an inquiry into whether Nunes disclosed classified information he learned from intelligence reports. At a news conference last month, Nunes said that communications involving associates of President Donald Trump had been swept up by U.S. spy agencies and, he suggested, mishandled by the Obama administration.

Watchdog groups said Nunes had apparently violated House rules by disclosing the existence of a foreign surveillance warrant.

Lawmakers "take an oath that they will not disclose classified information," said Fred Wertheimer, president of Democracy 21, a nonprofit that promotes government accountability and transparency. "The question is whether (Nunes) violated that oath or not."

Noah Bookbinder, executive of CREW, a separate watchdog group that files frequent ethics complaints, said he was grateful that the ethics panel responded quickly following the groups' complaint last week.

"We hope they do a serious investigation, do it quickly and come to a conclusive finding," said Bookbinder, adding that ethics investigations can sometimes become "a black hole" with little public accountability or transparency.

The ethics panel declined to comment beyond its one-page statement, but ethics probes can drag on for months or years before public resolution.

The panel has a range of options, from a finding of no wrongdoing to a letter of reproval, which amounts to a public scolding. The panel also could recommend that the full House vote on a reprimand or censure — or, more ominously, vote to expel Nunes. Expulsion would take a two-thirds vote of the House and is considered highly unlikely.

The last time the House voted to reprimand a lawmaker was 2012, when Rep. Laura Richardson, D-Calif., was cited and fined $10,000 for compelling congressional staff members to work on her re-election campaign.

The House censured Rep. Charles Rangel, D-N.Y., in 2010 for failure to pay income taxes and misuse of his office to solicit campaign donations.

In 1995, the ethics committee said Rep. Robert Torricelli, D-N.J., had acted in a manner "contrary" to House rules by providing classified information to the New York Times.

The inquiry by the full 10-member ethics panel could face one complication: Rep. Trey Gowdy, R-S.C., serves on the ethics committee and has been tapped by House Speaker Paul Ryan to help Conaway lead the Russia probe.

Gowdy, who led a two-year inquiry into the deadly attacks on a U.S. facility in Benghazi, Libya, could not be reached for comment Thursday. A spokeswoman did not immediately return telephone and email messages.