The return of Nunes could further inflame the partisan fervor surrounding the investigation into Russian meddling in the 2016 US elections.
The California Republican has already launched a joint investigation with the Oversight Committee of the House on the Uranium agreement One that was agreed in 2010 under the Obama administration, which Republicans claim involved illicit donations to the Clinton Foundation.
He has also criticized the FBI and the Justice Department for failing to deliver documents or present witnesses in response to subpoenas related to the FBI connection to the Fusion GPS opposition investigation file on President Donald Trump and Russia compiled by the Former British agent Christopher Steele.
The Ethics The committee announced on Thursday that it was closing its investigation into Nunes after determining that the information he had disclosed was not classified.
"In the course of this investigation, the Committee requested the analysis of the statements of Representative Nunes by experts in classification in the intelligence community, "the Ethics Committee said in a statement. "Based solely on the conclusion of these classification experts that the information revealed by Representative Nunes was not classified, the Committee will not take any action and will consider this matter closed."
In April, Nunes temporarily left aside his role as head of the committee's investigation into the meddling of Russian elections amid questions about his decision to provide information to the White House on the "unmasking" of officials of Trump at the end of the Obama administration.
Rep. Mike Conaway, a Republican from Texas, took the lead in the Russian investigation along with the committee's top Democrat, Adam Schiff of California.
But Nunes has participated in the investigation, since he has continued to sign the committee's citations as president, with the blessing of Conaway. Nunes has said for months that he had not departed from the investigation, but had temporarily moved away while the ethics panel's investigation was ongoing.
Focus on Clinton, Obama administration
Nunes' role has been a sensitive spot for Democrats on the committee, and research into Russian meddling and possibly collusion with the Trump campaign has been frequently shaken by partisan tensions.
Earlier this week, Nunes told CNN he still planned to go ahead by keeping FBI Director Chris Wray and Deputy Attorney General Rod Rosenstein in contempt of Congress for failing to comply with committee citations.
In a statement, Nunes accused the Democrats of the Ethics Committee of making statements that seemed to prejudge him, and asked the panel to "publicly publish all of his trans"
"Although I appreciate the work of the Ethics Committee, I need to reiterate that the accusations against me were obviously frivolous and rooted in politically motivated complaints filed against me by groups of left activists, "Nunes said. "I respect the ethics process, but I'm still dismayed because the Committee took an incredible eight months to dismiss this matter."
The ethics investigation was initiated on charges that he had discussed classified material after his clandestine meeting at the White. House in March on the unmasking of Trump officials.
Nunes has accused Obama administration officials of "unmasking" for political reasons or identifying US officials in documents compiled through foreign surveillance. Officials of the Obama administration have argued that they had legitimate reasons to unmask the requests they made.
It could be politically and logistically complicated for Nunes to completely regain control of the investigation.
The committee has spoken with dozens of witnesses since Nunes retired in April, while representatives Conaway, Trey Gowdy of South Carolina and Tom Rooney of Florida took the initiative to interview witnesses on the Republican side.
Conaway is already discussing the end of the game for the committee's investigation, with a report he hopes to write when the committee finishes interviewing the witnesses. Conaway has said he wants to conclude the investigation as soon as possible.
The spokespersons for Schiff and Conaway did not immediately respond to a request for comment.