By Mark Hosenball

WASHINGTON (Reuters) - President Donald Trump's son-in-law and adviser Jared Kushner on Thursday appeared at a closed door meeting of the U.S. Senate Intelligence Committee for the second time, four congressional sources said.

It was not known what topics were discussed with Kushner, who is involved in developing an Israeli-Palestinian peace plan and has helped forged closer U.S. ties with Saudi Arabia. The committee has been conducting a largely bipartisan investigation of suspected Russian interference in the 2016 U.S. election and the nature of contacts between Trump campaign members and Russian officials, including Kushner.

A spokesman for Kushner's lawyer Abbe Lowell did not immediately respond to a request for comment.

Senator Mark Warner, the panel's Democratic Vice Chairman declined to comment.

Senators and staff investigators were present at the meetingwith Kushner in a Senate office building, the congressional sources said. Kushner, who is married to Trump's daughter Ivanka Trump, had previously appeared before the panel in July 2017. Only staff investigators were present at that session, according to news reports at the time.

Committee investigators are working on a five-chapter final report on Russian political activities targeted at the United States and American responses to them. Russia denies interfering in the election. U.S. intelligence agencies concluded that Moscow meddled to undermine the U.S. democratic process and help Trump get elected.

U.S. Attorney General William Barr on Sunday released his four-page summary of Special Counsel Robert Mueller's report on a 22-month investigation into Russian interference in 2016. Barr said Mueller did not establish that Trump's campaign colluded with Russia in