To help the ongoing investigation into the claims of Russian influence in the U.S. presidential elections in November, Roger J. Stone Jr., an informal adviser to President Donald Trump has been asked to preserve all related records in his possession. The Senate Intelligence Committee notified Stone on Friday that he would be questioned as well, the New York Times reported.

Stone is reportedly under scrutiny by other federal investigators who have ordered him not to destroy any evidence he may have of Russians trying to meddle with the election process.

Read: Hacking Claims Hinder The Scope Of Improvement In US-Russia Relations in 2017

The letter sent to Stone by the Senate Intelligence Committee was dated Feb. 17. However, Stone said he received it Friday through an email. It was signed by the committee’s chairman Sen. Richard M. Burr (R-North Carolina) and its ranking Democrat, Sen. Mark Warner of Virginia, according to the Times.

After receiving the letter, which is the first public indication of the committee's inquiry into Trump's connections with Russia, Stone signaled he would cooperate in the inquiry and provide all possible information. But he reiterated that intelligence agencies cannot find any evidence of him conspiring with Russians against former Democratic presidential candidate, Hillary Clinton.

Trump's longtime confidant and former campaign adviser, Stone confessed March 10 that he had contacts with "Gucifer 2.0" — a self-described Romanian hacker who owned up to hacking into the Democratic National Committee's computer network and leaking its documents to the media and also to WikiLeaks.

Stone has been under close watch by Democrats and some investigators since August last year when he posted on Twitter about John D. Podesta , Clinton’s campaign chairman, whose private emails were hacked and provided to WikiLeaks. He later clarified he was referring to business activities he attributed to Podesta, and the tweet had nothing to do with prior knowledge of the hackings, the Times reported.

In October 2016, Stone had told a news channel that he had “back-channel communications” with WikiLeaks founder Julian Assange over the release of thousands of emails stolen from the Hillary Clinton campaign.

“I do have a back-channel communication with Assange, because we have a good mutual friend,” Stone said. “That friend travels back and forth from the United States to London and we talk. I had dinner with him last Monday.”