WASHINGTON (Reuters) - The Senate Intelligence Committee, investigating Russian meddling in U.S. 2016 election, has asked President Donald Trump’s political organization to hand over all documents going back the campaign’s launch in June 2015, the Washington Post reported on Friday, citing two people briefed on the request.  The letter from the Senate panel seeking all documents, emails and telephone records arrived at Trump’s campaign committee last week and was addressed to its treasurer, the Post said. This marked the first time the Trump campaign organization has been drawn into the bipartisan committee’s investigation into Russian interference in the presidential election, it said. Dozens of former campaign staffers are expected to be contacted soon to ensure they are aware of the request, the Post said, citing the two people. The letter was signed by Republican Senator Richard Burr, the committee’s chairman, and Senator Mark Warner, its top Democrat, according to the Post, which said representatives for Burr and Warner declined to comment. The Senate panel’s investigation is among several in Congress into Russian interference in the election, and is separate from a probe into the matter being led by a special counsel appointed last week by the Justice Department, former Federal Bureau of Investigation Director Robert Mueller. Trump’s campaign committee, based at Trump Tower in New York, is now led by Michael Glassner, a former deputy campaign manager, and John Pence, a nephew of Vice President Mike Pence, the Post said. Glassner did not immediately respond to a request for comment and a White House representative had no immediate comment, the Post said. Trump’s administration has been dogged by concerns about its ties to Russia and questions over whether Trump associates may have cooperated with Russians as they sought to meddle in last year’s election on Trump’s behalf. U.S. intelligence agencies concluded in January that Moscow tried to sway the November vote in Trump’s favor. Russia has denied involvement, and Trump has denied any collusion between his campaign and Russia. Controversy has engulfed Trump since he fired FBI Director James Comey on May 9 as Comey oversaw an investigation into possible collusion between his presidential campaign and Russia. 