WASHINGTON — The Senate intelligence committee has asked for documents from former presidential candidate Jill Stein as part of its probe into Russian interference in the 2016 election, adding another new thread to the panel’s investigation as it heads into 2018.

Stein said in a statement overnight Tuesday that she was cooperating with the probe and is providing documents to the committee. She has captured the interest of investigators partly because she attended a 2015 dinner sponsored by Russian television network RT with Russian President Vladimir Putin.

The Senate intelligence committee chairman, Richard Burr, R-N.C., appeared to confirm the investigation’s new focus on Stein Monday evening. Asked what the committee wanted to know about from Stein’s campaign, Burr responded: “collusion with the Russians.”

The request to Stein is more evidence that the Senate panel will still have much work to do in 2018. While the investigation has largely focused on both the Russian interference and whether it was in any way connected to President Donald Trump’s campaign, investigators are following multiple leads.

The top Democrat on the panel, Virginia Sen. Mark Warner, would not confirm the investigation into Stein but noted on Tuesday that she was at what he called the “infamous dinner” with Putin. Michael Flynn, who later became Trump’s national security adviser, also attended the 2015 dinner in Moscow. He is cooperating with special counsel Robert Mueller’s probe into the Russian meddling and has pleaded guilty to a count of making false statements to FBI agents.

Warner also said Stein had said complimentary things about Julian Assange, the founder of WikiLeaks, who Warner said “clearly was being used by the Russians to take some of the hacked information and release into our political system.”

WikiLeaks released stolen emails from several Democratic officials during the campaign. Assange denies receiving the material from Russia.

Stein ran against Trump and Democrat Hillary Clinton as a member of the Green Party and received about 1 percent of the vote. She said in the statement Tuesday the documents show that she “made the trip with the goal of reaching an international audience and Russian officials with a message of Middle East peace, diplomacy and cooperation against the urgent threat of climate change, consistent with long-standing Green principles and policies.”

As the Senate investigation continues, the House intelligence committee is working to wrap up its own probe into the meddling early next year. Investigators are interviewing multiple people this week in hopes that they will finish most of that work before the end of the year. A final report — or two final reports, if Democrats decide to write their own — could come in early 2018.

The House intelligence committee is interviewing FBI Deputy Director Andrew McCabe on Tuesday as Republicans have charged political bias among the ranks of the FBI. They have focused on hundreds of text messages between an FBI counterintelligence agent and an FBI lawyer that show the officials using words like “idiot” and “loathsome human” to characterize Trump as he was running for president in 2016.

Peter Strzok, a veteran FBI counterintelligence agent, was removed from Mueller’s team over the summer following the discovery of the text messages exchanged with Lisa Page, an FBI lawyer who was also detailed to the group of agents and prosecutors investigating potential coordination between Russia and Trump’s Republican campaign.

The messages were reviewed by The Associated Press.