After weeks of silence, former Atlanta U.S. Attorney Sally Yates is expected to talk to members of Congress about contacts between Russia and members of the Trump administration during the presidential transition period.
Yates will testify before a Senate panel Monday.
She was acting U.S. attorney general in the final months of the Obama administration and in the early days of Donald Trump's presidency.
CNN is quoting sources as saying Yates will testify that she gave officials in the new Trump administration a stern warning that then-National Security Adviser Michael Flynn lied when he denied he discussed U.S. sanctions on Russia with Sergei Kislyak, the Russian ambassador to the U.S.
According to CNN's sources, Yates told White House counsel that Flynn's misleading statements could make him vulnerable to Russia.
Flynn was fired Feb. 13.
This will be the first time Yates has publicly spoken on the issue.
But because some of her testimony will involve classified information, it's expected she won't be able to give much detail about what led to her concerns about Flynn.