Updated at 3:45 p.m. ETNational Security Adviser Michael Flynn's contacts with Russia's ambassador to the U.S. in December included a discussion of U.S. sanctions imposed by then-President Barack Obama, according to new reports that contradict what the White House has said about the matter.The sanctions included the expulsion of 35 Russian diplomats; when they were announced in late December, they drew a notably muted response — and no retaliation — from Moscow.Citing current and former U.S. officials, The Washington Post reports, "Flynn's communications with Russian Ambassador Sergey Kislyak were interpreted by some senior U.S. officials as an inappropriate and potentially illegal signal to the Kremlin that it could expect a reprieve from sanctions that were being imposed by the Obama administration in late December to punish Russia for its alleged interference in the 2016 election."The question of the contacts' legality largely rests in the Logan Act, which bans unauthorized U.S. citizens from communicating with a foreign government "with intent to influence the measures or conduct of any foreign government ... in relation to any disputes or controversies with the United States, or to defeat the measures of the United States."The Logan Act was passed in 1799 — but there are no recorded prosecutions under the law.It's been known that Flynn had contacts — text messages and at least one phone conversation — with the Russian ambassador before President Trump's inauguration. The White House has said nothing improper took place, although its explanations for those contacts have shifted.In an interview this week, Flynn twice flatly denied discussing sanctions with Kislyak, the Post says. But the newspaper adds that Flynn's spokesman later gave a more nuanced response, saying that Flynn "indicated that while he had no recollection of discussing sanctions, he couldn't be certain that the topic never came up."The topic has evolved over time: When NPR's Tamara Keith reported on the issue on Jan. 13, she said, "Sean Spicer, the spokesman and incoming White House press secretary, insisted all of this contact happened before President Obama announced the retaliation, and, as a result, Obama's move to expel 35 Russian diplomats wasn't a topic of conversation."Those sanctions were announced on Dec. 29; within hours of saying all of Flynn's contact with Kislyak had taken place on Dec. 28, Spicer clarified to NPR that a phone call between Flynn and Kislyak had taken place "around the same time" the retaliation was announced. As to whether the two discussed the U.S. sanctions and/or a potential Russian response, Spicer told Tamara it was "doubtful."After Obama imposed the sanctions, a retaliation seemed certain. Russia's Foreign Ministry mocked the U.S. president online and recommended an in-kind expulsion of 35 American diplomats. But Russian President Vladimir Putin said, "We will not expel anyone" — and invited the children of U.S. diplomats to visit the Kremlin's Christmas tree, as NPR's Lucian Kim reported.Lucian added, "Putin said in his statement he will work to restore Russian-U.S. relations based on the policies of incoming President Donald Trump."On Sunday talk shows last month, when Vice President Pence was asked about the controversy, he said on CBS's Face the Nation that it was "strictly coincidental" that Flynn and the ambassador spoke around the time the sanctions were levied — and, he added, "they did not discuss anything having to do with the United States' decision to expel diplomats or impose censure against Russia."Today, an administration official tells NPR and other news outlets that Pence had based his response on conversations he had with Flynn as he prepared to appear on the show.Responding to the most recent reports about Flynn, California Rep. Adam Schiff, the top Democrat on the House Intelligence Committee, said the allegation that Flynn might have secretly discussed ways to undermine U.S. sanctions "raises serious questions of legality and fitness for office." And if Flynn or other officials have misled the public about the matter, Schiff said, "his conduct would be all the more pernicious, and he should no longer serve in this Administration or any other."As the story of Flynn's contacts with Kislyak emerged last month, the Senate Select Committee on Intelligence announced it would investigate allegations that Russia meddled in the U.S. elections; the FBI has also been looking at the charges.The ranking Democrat on that Senate panel, Sen. Mark Warner, released a statement Friday saying the new reports "underscore both the gravity and the urgency" of its investigation.NPR's Mary Louise Kelly, who's filing a story on the Flynn allegations for today's All Things Considered, says she has reached out to senior Republicans on the House and Senate Intelligence committees. Rep. Devin Nunes of California declined comment through a spokesman. As of Friday afternoon, she hadn't heard back from Sen. Richard Burr of North Carolina.Pence and others in the incoming administration dismissed reports that members of the Trump team had been in touch with Russian officials during the presidential campaign. Shortly after the election, Russian Deputy Foreign Minister Sergei Ryabkov was quoted telling a news agency, "I don't say that all of them, but a whole array of them, supported contacts with Russian representatives."Flynn's relationship with Russia has drawn questions before — particularly after the former head of the Defense Intelligence Agency shared a table with Russian President Vladimir Putin at a gala in Moscow for the state-run news channel Russia Today.On Friday, the Kremlin delivered a rather unenthusiastic denial of the Post's story.Kremlin spokesman Dmitry Peskov, reports state-run TASS media, "said his understanding is that 'there were certain conversations (between Flynn and Kislyak)', though 'it is better to double check the information in the Foreign Ministry.""Other than that the information is not correct," Peskov added, according to TASS. Copyright 2017 NPR. To see more, visit http://www.npr.org/.