A second official said the justice department was concerned Mr Flynn could be in a compromised position as a result.
The crisis over the relationship between United States President Donald Trump's aides and Russian Federation deepened yesterday as a growing number of Mr Trump's fellow Republicans demanded expanded congressional inquiries into the matter.
A Kremlin spokesperson said Monday that Flynn, who had already received criticism for a photo of him sitting near Russian President Vladimir Putin at a 2015 banquet, did not discuss the lifting of sanctions with Kislyak.
Gen Flynn resigned on Monday - less than a month into the job - after he allegedly discussed U.S. sanctions against Moscow with Russian ambassador Sergey Kislyak in a phone call late previous year. Chris Christie on Wednesday defended President Donald Trump's administration after Michael Flynn resigned as Trump's national security adviser following reports that he misled Vice President Mike Pence about his contacts with Russian Federation.
Yates advised the White House that Flynn may have violated the Logan Act, which pertains to the dealings of United States citizens with foreign countries.
House Speaker Paul Ryan said Flynn made the right decision to step down.
Question: "Did you fire Mike Flynn?".
Senate Intelligence committee chairman Richard Burr, R-N.C., said his panel plans "to continue to do aggressive oversight on the committee privately".
But the press secretary insisted Gen Flynn had stepped down over a "matter of trust" rather than a legal issue.
After the US sanctions were announced, Russian President Vladimir Putin took the uncharacteristic step of announcing he would not respond in kind, and instead he invited USA diplomats in Moscow to join Christmas celebrations at the Kremlin.
Asked after a rambling speech in which he repeated a number of falsehoods, including the number of electoral college votes he got, if he was concerned about undermining the publics faith in the First Amendment and freedom of the press by calling stories he doesn't like "fake news", Trump said he wanted to see an "honest press".
"It's obvious that Flynn was forced to write the letter of resignation under a certain amount of pressure", said Leonid Slutsky, the head of the lower house of parliament's foreign affairs committee, as reported by the government-run RIA news agency.
Question: "Mr. President, very simply you said today that you had the biggest electoral margin since Ron Reagan".
Lawmakers involved said they want to move quickly, but thoroughly, on the Russian Federation investigation. Sen. In fact, president Obama had 365, George Bush 426 when he won.
Flynn wasn't the only Russian Federation proponent in the administration. "We are and will remain in compliance with judicial orders", said a spokesperson.
Congressional Democrats expressed alarm at the developments surrounding Flynn and called for a classified briefing by administration officials to explain what had happened.