Mueller was appointed special counsel by the Department of Justice in the Russian Federation investigation in May after Trump fired FBI Director James Comey.
Two sources warned, however, that the information was not conclusive, according to CNN. It lapsed previous year, but the Federal Bureau of Investigation renewed the warrant into at least early 2017. But as Lawfare explains, even if Trump was picked up, "incidental collection" of that sort happens routinely during the course of criminal and counterintelligence investigations. In fact, that accusation is why Manafort left the Trump campaign back in August of 2016, after reports of the connections surfaced.
It isn't clear whether Mr. Trump himself was ever heard on the government's surveillance of Manafort. However, wiretapping had taken place during periods when Manafort was known to be in touch with President Donald Trump. Second, it raises the possibility that the feds have tapes that could contain direct evidence of Manafort, and possibly President Trump, talking about collusion with Russian Federation.
The unusual pace and aggression with which Mueller is moving against Manafort is a classic sign that the special counsel wants to coerce Manafort's cooperation in the Russian Federation probe, wrote former federal prosecutor Renato Mariotti. The FBI raided Manafort's home in July.
The question remains, said Napolitano, if investigators were listening to Manafort to learn what Trump was going to do next in his campaign, and if the information was going to be used to help Democratic nominee Hillary Clinton.
Sources say the FBI investigation initially centered on work done by Washington consulting firms working for Ukraine's former ruling party. Some of the conversations listened to were reportedly with US President Donald Trump after he was elected.
Manafort pulled ahead on Monday night with the release of two explosive reports that revealed he's been intermittently under federal surveillance since 2014, and special counsel Robert Mueller's prosecutors recently told him that they plan to indict him.
Later that month, then-FBI Director James Comey disputed Trump's claims to the House intelligence committee.
Russian Federation has denied interfering in the election and Trump has denied there was collusion. Asked directly whether there was a FISA warrant to tap Trump's phone at Trump Tower, Clapper responded bluntly: "I can deny it".