As lawmakers' investigations of Russian meddling in the 2016 election continue to press forward, Rep. Adam Schiff, D-California, says that there is "no truth" to the claim that President Obama had wiretapped then-candidate Donald Trump at Trump Tower during the campaign, in light of new reports that Trump campaign manager Paul Manafort was wiretapped.

"Not only did Director Comey and Director Mike Rogers of the NSA say there was no truth to the president being wiretapped at Trump Tower, but the Department of Justice recently confirmed that was false as well," Schiff said on CBS News' "Face the Nation" Sunday.

"I can't comment on whether Mr. Manafort was ever the subject of surveillance of any kind," he added. "Even if he were, though, that doesn't justify or suggest that the president was wiretapped improperly by Barack Obama, so there's no truth to that."

Schiff's comments come after CBS News confirmed that Manafort was being monitored by the FBI at the time.

"The allegation that he [Manafort] was reaching out to Russian oligarchs close to Putin, and suggesting that he would offer them useful information to them while he was campaign manager, at the very same time the Russians are reaching out to him to offer information on Hillary Clinton," Schiff said. "That is of deep concern to us."

That surveillance dates back to before Robert Mueller was appointed as special counsel to take over the investigation from the FBI.

According to CNN, which first reported the Manafort monitoring, the FBI began the surveillance in 2014, as a result of consulting work done by Washington firms for the pro-Russian party of former Ukrainian President Viktor Yanukovych.

The U.S. government listened in on Manafort's conversations during the presidential campaign and through the election -- though not constantly -- and its surveillance includes the period when Manafort was Mr. Trump's campaign chairman.

As the investigation moves forward, the top ranking Democrat on the House Intelligence Committee also called into question social media's role in the 2016 election, particularly as it relates to Russian influence in the election's results.

"There's a lot we don't know yet about it. I think we know only the minimum of the advertising. And, of course, advertising was only one method the Russians used on social media, and this was only one platform," said Schiff.

Facebook founder Mark Zuckerberg announced on Thursday the company is cooperating with Congress' probe by providing details into ads purchased by Russian entities over the course of the campaign.

Schiff added, "But there's also an issue about the use of Facebook's algorithms and the way it tends to potentially reinforce people's informational bias. And this is a problem that goes well beyond Russia."

He told CBS News that Russia used algorithms to "amplify misinformation or slated information" in an effort to bolster then-candidate Trump. He noted however, "it's far broader, and we have to ask, "Is this in our society's interest to create these informational silos?"