(Reuters) - Republican lawmaker Devin Nunes’ investigation into whether Obama administration officials used classified intelligence reports to discredit Donald Trump’s 2016 campaign team could backfire on the congressman - and the president, sources familiar with the reports said.

File Photo: Devin Nunes speaks to reporters on Capitol Hill in Washington, U.S., March 29, 2017. REUTERS/Joshua Roberts

The reports contain no evidence that any aides to former Democratic President Barack Obama acted improperly, the sources said, but they do indicate some Trump associates may have violated an obscure 1799 law, the Logan Act, which prohibits unauthorized U.S. citizens from negotiating with a foreign government that has a dispute with the United States.

The spying reports also are relevant to the investigation by special counsel Robert Mueller into conclusions by U.S. intelligence agencies that Russia worked to tilt last November’s election in Republican Trump’s favor, said the sources, who spoke on the condition of anonymity.

Mueller’s office declined to comment.

Russia, under U.S. sanctions for rights abuses and its 2014 annexation of Crimea, has repeatedly denied allegations of election meddling. Trump has denied any possible collusion between his campaign and Moscow, an issue that has loomed over the new presidency.

Nunes, chairman of the U.S. House Intelligence Committee and a Trump ally, met secretly earlier this year with a White House intelligence aide and then accused Obama officials of having requested the names of U.S. citizens seen in intercepts of communications with Russians and other foreigners.

The White House did not respond to requests for comment.

The names would have been routinely censored from intelligence agency intercepts, but Nunes charged that Obama’s aides had leaked the information to try to undermine Trump while he was running for president.

A spokesman for then-United Nations ambassador Samantha Power, whom Nunes and other Republicans accused of digging for political dirt, said she read intelligence reports only as part of her normal duties. A spokesman for former Obama national security adviser Susan Rice, whom Republicans also accused of misusing intelligence, did not respond to requests for comment.

Mueller is investigating meetings and conversations between Trump associates and Russian and other foreign officials and businessmen. They include Trump’s adviser and son-in-law Jared Kushner; the president’s eldest son Donald Trump, Jr.; former Trump campaign chairman Paul Manafort and former national security adviser Michael Flynn.

“An obvious question is how all these meetings and conversations were set up,” said one of the sources. “Who set them up? What was their purpose? What were the agendas? Who approved them? Who was briefed on them afterward? Signals intelligence might shed some light on that.”

Representatives for the Trump associates did not respond to requests for comment.

Democratic lawmakers have said that Nunes and others have made the assertions about the leaks to distract attention from two congressional investigations and Mueller’s probe into the Russian matter.

The National Security Agency masks the names of U.S. citizens in intercepts, but officials with the necessary security clearances can request them for intelligence purposes.

“Unmasking Americans is extremely sensitive, and unmasking political opponents is really problematic,” said a congressional official, also speaking on the condition of anonymity. If Obama officials asked for the names or failed to justify any requests, that warranted investigation, the official said.

Asked for hard evidence that Power or other aides misused intelligence for political purposes or leaked such information to the media, the official declined to comment.