Facebook launched an investigation into "suspicious" content praising Bernie Sanders after receiving a tipoff from an outside researcher, The Wall Street Journal reported.

The company did not find any evidence that the behavior was inauthentic.

Officials have told Sanders that his campaign may be benefiting from Russian interference, and President Donald Trump called on Sunday for Democrats to investigate.

Officials have also briefed that Trump's campaign is being aided by Russia.

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Facebook has been investigating "suspicious" content supporting Democratic candidate Bernie Sanders, The Wall Street Journal reported.

The tech giant started investigating after getting tipped off by a researcher, and some members of Facebook's leadership team were briefed, sources told the Journal.

The investigation did not yield any evidence that the accounts in question were inauthentic.

"We investigate each credible claim we receive, just as we did in this instance when an outside researcher contacted us. To date, we have not been able to substantiate the researcher's claims and we have not been notified by the intelligence community," a Facebook spokesman told the Journal.

"Had we found a campaign of coordinated inauthentic behavior, we would've removed it and announced it publicly, just as we did more than 50 times last year," he added. Another Facebook spokesman repeated this statement to Business Insider.

Sanders, who is the frontrunner for the Democratic presidential nomination following his strong performance in early-voting states, has become a focal point for concerns about Russian election interference.

The Washington Post reported last week that officials briefed Sanders that the Russian government is trying to help his nomination campaign.

An election-security official also told lawmakers that Russian interference was being deployed to help President Trump's campaign.

Sanders told the Post that the Russian interference could swing both ways, and could be behind some "ugly" attacks on social media attributed to his supporters.

"In 2016, Russia used internet propaganda to sow division in our country, and my understanding is that they are doing it again in 2020. Some of the ugly stuff on the internet attributed to our campaign may well not be coming from real supporters," said Sanders.

President Trump on Sunday called on Democrats to investigate whether "Russia, Russia, Russia" is working to help Sanders.