Also on Monday, CNN reported that USA law enforcement had wiretapped Manafort under a Foreign Intelligence Surveillance Act (FISA) warrant as early as 2014, when he came under investigation by the F.B.I. for work that he conducted as a political consultant for the pro-Kremlin Party of Regions in Ukraine.
CNN's sources suggested that some of the evidence "sparked concerns among investigators that Manafort had encouraged the Russians to help with the campaign", but that the evidence of Russian collusion remained inconclusive. Two, however, warned the evidence is inconclusive.
It noted that in 2014, Manafort was surveilled under a separate FISA authorization as the Federal Bureau of Investigation scrutinized his lobbying work on behalf of the pro-Russia Party of Regions in Ukraine and his business dealings with Russian entities. Instead, investigators needed only to show justifiable suspicion that Manafort may have been working as a foreign agent.
Manafort came under fire over his work in the Ukraine with the party of former President Viktor Yanukovych, and as a result, surveillance of Manafort reportedly commenced through the Foreign Intelligence Surveillance Act.
CNN's sources said that the second warrant, the start date of which is unknown, was based on efforts to investigate possible ties between Trump campaign associates and Russian agents.
The surveillance became part of the FBI's probe into alleged cooperation between members of the Trump campaign and Russian Federation to affect the results of the 2016 presidential elections in the US. Manfort was Donald Trump's campaign manager at the time of the 2016 USA presidential elections.
We do not know if the government's surveillance of Manafort included Trump Tower. But during that time, while he was Donald Trump's campaign manager, several communications emerged that caught the attention of the federal government between Manafort and Russian officials, which led them to believe that Manafort might be trying to work with the Russians in order to influence the outcome of the 2016 election.
A spokesperson for Mueller did not immediately respond to a BuzzFeed News request for comment.
The FBI was looking for evidence that Manafort had maintained a secret offshore bank account - possibly to obtain money from Russian operatives. Mr. Mueller's team also took the unusual step of issuing a subpoena to Melissa Laurenza, a specialist in lobbying law who formerly represented Mr. Manafort. It is unclear whether the President was recorded as part of the investigation. Manafort was sacked from the campaign months before Election Day, but continued to communicate with Trump into his presidency.
According to The New York Times, which cited two people it said were close to the case, USA agents informed Manafort on September 18 that they planned to indict him when they raided his home in Virginia in July.