WASHINGTON — The House Ethics Committee announced Thursday that it has closed its investigation into whether Intelligence Committee Chairman Devin Nunes violated any laws or congressional rules by disclosing classified information.

The Ethics Committee's decision to end its probe means that Nunes is free to resume leadership of the Intelligence Committee's investigation into Russian interference in the 2016 presidential election. It was not immediately clear Thursday night if Nunes would choose do so.

The California Republican temporarily stepped aside from the Russia investigation in April because of the ethics probe, which launched after Nunes took a secret trip to White House grounds last spring to review information gathered by unnamed sources purporting to show that President Trump was under surveillance by the Obama administration during the 2016 campaign.

More: Democrats say House Intel Committee Republicans are trying to thwart Russia probe

More: Devin Nunes temporarily steps aside in Russian meddling probe

At a news conference after his trip, Nunes told reporters that he had discovered evidence to support the president's claim that he was wiretapped at Trump Tower. However, the Justice Department confirmed in a court filing in September that there was no evidence that Trump Tower was targeted for surveillance.

In a joint statement Thursday, Ethics Committee Chairman Susan Brooks, R-Ind., and Rep. Ted Deutch of Florida, the panel's senior Democrat, said the committee based its decision to close the case against Nunes on a review by experts in the Intelligence Community about what constitutes classified information.

"The Committee does not determine whether information is or is not classified," the statement said. "In the course of this investigation, the Committee sought the analysis of Representative Nunes’s statements by classification experts in the intelligence community. Based solely on the conclusion of these classification experts that the information that Representative Nunes disclosed was not classified, the Committee will take no further action and considers this matter closed."

Nunes thanked the committee Thursday night "for completely clearing me today of the cloud that was created by this investigation, and for determining that I committed no violation of anything — no violation of House Rules, law, regulations, or any other standards of conduct.

"While I appreciate the Ethics Committee’s work, I need to reiterate that the allegations against me were obviously frivolous and were rooted in politically motivated complaints filed against me by left-wing activist groups," Nunes said. "I respect the ethics process, but I remain dismayed that it took an  unbelievable eight months for the Committee to dismiss this matter."

The "left-wing" groups that Nunes was referring to include MoveOn.Org, Citizens for Responsibility and Ethics in Washington (CREW) and Democracy 21.

Nunes called on the Ethics Committee to publicly release all transcripts of his case.

"The Committee can work with me and my staff to ensure that any necessary protocols regarding classified information be adopted prior to any such release," Nunes said. "Both this House and the American people would undoubtedly benefit from such an act of transparency and accountability to bolster confidence that partisanship does not infect the Ethics Committee’s investigations."

Nunes has been at odds with Democrats on the Intelligence Committee, who are upset that he has continued to issue subpoenas for documents and witnesses despite saying that he had stepped aside from the probe. Nunes, a Trump ally, has focused his own inquiries on actions by former Democratic presidential candidate Hillary Clinton and the Obama administration.

Nunes said he was concerned by public statements made by four of the Ethics Committee's five Democrats that "appeared to prejudge this matter before they began investigating the complaint."

He also said he was concerned about the "unprecedented step" the Ethics Committee took in investigating his alleged disclosure of classified information when such allegations have historically been reviewed by non-partisan professional staff from the intelligence committee.

More: House Republicans launch two new investigations tied to Hillary Clinton

More: Grassley reveals deep partisan split in Senate Judiciary Committee's Russia probe