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FBI, CIA, and NSA agents have investigated communications between retired Lt. Gen. Michael Flynn, President Trump's national security adviser, and Russian officials to determine if the contact may have violated laws, people familiar with the matter told The Wall Street Journal.

It's unclear when the inquiry began or whether any incriminating evidence has been found. Flynn plays a role in setting U.S. policy toward Russia, and the probe is looking into a series of calls Flynn made to the Russian ambassador to the United States, Sergey Kislyak, on Dec. 29, the day the Obama administration announced sanctions against Russia for interfering with the 2016 presidential election. Read more about the investigation at The Wall Street Journal.