Michael Flynn. AP Photo/Carolyn Kaster Donald Trump's transition team did not believe former national security adviser Michael Flynn appreciated the risks of his communications with Russia ahead of Trump's inauguration, The Washington Post reported on Friday.

Flynn had apparently been warned about contacts he had with Russian ambassador Sergey Kislyak — communications that were certain to have been monitored by US intelligence agencies, according to US officials cited by The Post.

The Trump transition teams apparently deemed the matter serious enough to ask the Obama administration for a classified CIA report on Kislyak to share with Flynn.

"The document was delivered within days, officials said, but it is not clear that Flynn ever read it," The Post's Greg Miller and Adam Entous wrote.

Those warnings from the Trump transition team's national security staff to Flynn came one month before Flynn was captured on recordings discussing newly issued US sanctions against Russia, The Post reported. The Obama administration had leveled those sanctions in response to Russia's meddling in the US presidential election.

Just 24 days into his job as Trump's national security adviser, Flynn was forced to resign for misleading Trump administration officials about his communications with Kislyak.

Flynn is just one piece of a growing puzzle in a multi-agency investigation of ties between Russia and people in Trump's orbit. A bipartisan inquiry is underway in the House and Senate, and the FBI is also investigating. Former Deputy Attorney General Sally Yates warned the White House in January that Flynn might be at risk of Russian blackmail, according to a CNN report published this week.

Yates was fired by the Trump administration that same month for defying the president's controversial travel ban.

Yates is set to testify before the Senate Intelligence Committee to discuss warnings about Flynn that she gave to the White House. She reportedly told White House Counsel Don McGahn that she had "serious concerns" about Flynn, but Flynn was not asked to resign until February 13, at least two weeks after Yates visited the White House.