According to the newspaper, the investigation's goal was to discover the nature of Flynn's contacts with Russian officials and the degree of their compliance with law.
The inquiry reportedly focused on the telephone call Flynn made to Russian Ambassador to the United States Sergey Kislyak on December 29, 2016, when the latter invited Flynn to participate in the peace talks on Syria in Astana.
The White House reportedly denied any knowledge of a probe or even any grounds for an investigation.
Flynn would not be the only member in Trump's administration whose links to Russia have faced intense scrutiny. Trump's pick for Secretary of State Rex Tillerson had to report in detail on his prospective policy regarding Russia at his confirmation hearing amid media questioning his ties to Moscow.
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