The FBI monitored social media on Election Day in November to track a suspected disinformation campaign by Russia that involved "fake news" articles, CNN reported Friday.
"Minor issues popped up in far-flung parts of the country, from Alaska to Georgia," the cable network said in its report, citing "multiple sources."
On Nov. 8, dozens of FBI agents and analysts worked at a command center in Washington laden with large monitoring screens as they watched for security threats, CNN reported.
However, another group of FBI counterintelligence analysts and investigators watched Facebook, Twitter and other social media.
Authorities had identified social media user accounts that were behind various stories, CNN reported.
Some of the users were based overseas, raising suspicions that they were part of a Moscow disinformation effort, two sources told the network.
Every three hours that day, investigators at the FBI, Homeland Security Department and the Office of National Intelligence talked with a team in the Situation Room of the White House on possible problems, CNN reported.
The FBI declined to comment on the report.
"We were right on the edge of constitutional legality," a person briefed on the investigation told CNN. "We were monitoring news."