Donald Trump’s top presidential transition officials reportedly warned former national security adviser Michael Flynn about his contacts with Russia’s U.S. ambassador “weeks” before they talked again in December. The Washington Post reports Flynn was informed that U.S. intelligence services were likely monitoring his communications with Sergey Kislyak, the Russian ambassador. The warning came before Flynn’s call with Kislyak in which he discussed the possibility of lifting sanctions against Russia when Trump would take office. Flynn misled Vice President Mike Pence and other top White House officials about the substance of that phone call, leading to his resignation in February. The Post also reported that a top national security official on the Trump transition, Marshall Billingslea, asked the Obama administration for a CIA profile of Kislyak due to their concerns about him. According to the Associated Press, Billingslea was concerned that Flynn “did not fully understand” Kislyak’s alleged connections to Russian intelligence services. An Obama adviser told the AP that the former administration delayed informing Trump’s team of its decision to impose sanctions on Russia, out of fear that they would “tip off Moscow.” The Obama team was also reportedly informed that Trump transition officials were making copies of classified documents at the transition headquarters and taking them elsewhere, prompting Obama aides to require that some documents be viewed at the White House. Last month, lawmakers revealed the Flynn did not disclose payments from Russia and Turkey on his security clearance application, in likely violation of the law.