Washington (CNN) US investigators wiretapped former Trump campaign chairman Paul Manafort under secret court orders before and after the election, sources tell CNN, an extraordinary step involving a high-ranking campaign official now at the center of the Russia meddling probe. 
 
 The government snooping continued into early this year, including a period when Manafort was known to talk to President Donald Trump. 
 
 Some of the intelligence collected includes communications that sparked concerns among investigators that Manafort had encouraged the Russians to help with the campaign, according to three sources familiar with the investigation. Two of these sources, however, cautioned that the evidence is not conclusive. 
 
 Special counsel Robert Mueller's team, which is leading the investigation into Russia's involvement in the election, has been provided details of these communications. 
 
 A secret order authorized by the court that handles the Foreign Intelligence Surveillance Act (FISA) began after Manafort became the subject of an FBI investigation that began in 2014. It centered on work done by a group of Washington consulting firms for Ukraine's former ruling party, the sources told CNN. 
 
 The surveillance was discontinued at some point last year for lack of evidence, according to one of the sources. 
 
 The FBI then restarted the surveillance after obtaining a new FISA warrant that extended at least into early this year. 
 
 Sources say the second warrant was part of the FBI's efforts to investigate ties between Trump campaign associates and suspected Russian operatives. Such warrants require the approval of top Justice Department and FBI officials, and the FBI must provide the court with information showing suspicion that the subject of the warrant may be acting as an agent of a foreign power. 
 
 It is unclear when the new warrant started. The FBI interest deepened last fall because of intercepted communications between Manafort and suspected Russian operatives, and among the Russians themselves, that reignited their interest in Manafort, the sources told CNN. As part of the FISA warrant, CNN has learned that earlier this year, the FBI conducted a search of a storage facility belonging to Manafort. It's not known what they found. 
 
 The conversations between Manafort and Trump continued after the President took office, long after the FBI investigation into Manafort was publicly known, the sources told CNN. They went on until lawyers for the President and Manafort insisted that they stop, according to the sources. 
 
 It's unclear whether Trump himself was picked up on the surveillance. 
 
 The White House declined to comment for this story. A spokesperson for Manafort didn't comment for this story. 
 
 Manafort previously has denied that he ever "knowingly" communicated with Russian intelligence operatives during the election and also has denied participating in any Russian efforts to "undermine the interests of the United States." 
 
 The FBI wasn't listening in June 2016, the sources said, when Donald Trump Jr. led a meeting that included Manafort, then campaign chairman, and Jared Kushner, the President's son-in-law, with a Russian lawyer who had promised negative information on Hillary Clinton. 
 
 That gap could prove crucial as prosecutors and investigators under Mueller work to determine whether there's evidence of a crime in myriad connections that have come to light between suspected Russian government operatives and associates of Trump. 
 
 Origins of the FBI's interest in Manafort 
 
 The FBI interest in Manafort dates back at least to 2014, partly as an outgrowth of a US investigation of Viktor Yanukovych, the former Ukrainian president whose pro-Russian regime was ousted amid street protests. Yanukovych's Party of Regions was accused of corruption, and Ukrainian authorities claimed he squirreled millions of dollars out of the country. 
 
 Investigators have spent years probing any possible role played by Manafort's firm and other US consultants, including the Podesta Group and Mercury LLC, that worked with the former Ukraine regime. The basis for the case hinged on the failure by the US firms to register under the US Foreign Agents Registration Act, a law that the Justice Department only rarely uses to bring charges. 
 
 All three firms earlier this year filed retroactive registrations with the Justice Department. 
 
 It hasn't proved easy to make a case. 
 
 Last year, Justice Department prosecutors concluded that there wasn't enough evidence to bring charges against Manafort or anyone of the other US subjects in the probe, according to sources briefed on the investigation. 
 
 The FBI and Justice Department have to periodically seek renewed FISA authorization to continue their surveillance. 
 
 As Manafort took the reins as Trump campaign chairman in May, the FBI surveillance technicians were no longer listening. The fact he was part of the campaign didn't play a role in the discontinued monitoring, sources told CNN. It was the lack of evidence relating to the Ukraine investigation that prompted the FBI to pull back. 
 
 Renewed surveillance 
 
 Manafort was ousted from the campaign in August. By then the FBI had noticed what counterintelligence agents thought was a series of odd connections between Trump associates and Russia. The CIA also had developed information, including from human intelligence sources, that they believed showed Russian President Vladimir Putin had ordered his intelligence services to conduct a broad operation to meddle with the US election, according to current and former US officials. 
 
 The FBI surveillance teams, under a new FISA warrant, began monitoring Manafort again, sources tell CNN. 
 
 The court that oversees government snooping under FISA operates in secret, the surveillance so intrusive that the existence of the warrants only rarely become public. 
 
 For that reason, speculation has run rampant about whether Manafort or others associated with Trump were under surveillance. The President himself fueled the speculation when in March he used his Twitter account to accuse former President Barack Obama of having his "wires tapped" in Trump Tower. 
 
 The Justice Department and the FBI have denied that Trump's own "wires" were tapped. 
 
 While Manafort has a residence in Trump Tower, it's unclear whether FBI surveillance of him took place there. 
 
 Manafort has a home as well in Alexandria, Virginia. FBI agents raided the Alexandria residence in July. ||||| A top lawyer for President Trump slammed the special counsel’s office over the FBI raid of former campaign manager Paul Manafort’s Virginia home, accusing investigators of committing a “gross abuse of the judicial process” for the sake of “shock value” – and employing tactics normally seen “in Russia not America.” 
 
 Trump attorney John Dowd leveled the complaints in an email sent to a Wall Street Journal reporter who wrote about the Manafort raid. The email was obtained by Fox News. 
 
 The email reflects Trump’s legal team moving to protect the president, amid speculation that the raid could be part of a broader effort to squeeze Manafort for information on Trump. 
 
 "These methods are normally found and employed in Russia not America.” - John Dowd, attorney for President Trump 
 
 Dowd, in his note, questioned the validity of the search warrant itself, calling it an “extraordinary invasion of privacy.” Dowd said Manafort already was looking to cooperate with congressional committees and said the special counsel never requested the materials from Manafort. 
 
 MANAFORT HOME RAIDED BY FEDS 
 
 “These failures by Special Counsel to exhaust less intrusive methods is a fatal flaw in the warrant process and would call for a Motion to Suppress the fruits of the search,” Dowd wrote, arguing the required “necessity” of the warrant was “misrepresented to the Court which raises a host of issues involving the accuracy of the warrant application and the supporting FBI affidavit.” 
 
 Dowd also said agents seized “privileged and confidential materials prepared for Mr. Manafort by his counsel to aid him in his cooperation with the Congressional committees,” adding: 
 
 “Thus, it appears the Search Warrant here was obtained by a gross abuse of the judicial process by the Special Counsel's office. In addition, given the obvious unlawful deficiencies, this extraordinary invasive tool was employed for its shock value to try to intimidate Mr. Manafort and bring him to his needs. These methods are normally found and employed in Russia not America.” 
 
 The special counsel’s office declined to comment when reached by Fox News. 
 
 It was revealed Wednesday that FBI agents had raided Manafort’s Virginia home in late July, one day after he met voluntarily with members of the Senate Intelligence Committee. 
 
 The search warrant seems to indicate that investigators may have had reason to believe Manafort could not be trusted to turn over all of the records sought, The Washington Post reported. 
 
 Manafort resigned as Trump’s campaign manager in August 2016 amid questions regarding his business dealings in Ukraine. Special Counsel Robert Mueller has taken over a criminal investigation into Manafort’s financial dealings, which began even before the 2016 election, as he probes Russian meddling in the campaign and possible coordination with Trump associates. 
 
 Trump has tried to distance himself from Manafort, though the relationship between the two goes back years. 
 
 Andrew Napolitano, senior judicial analyst for Fox News, said Wednesday on “Outnumbered” that the raid indicates the FBI did not trust that Manafort would preserve the materials they wanted. Further, he speculated the pressure on Manafort could ultimately be part of an effort to get to Trump. 
 
 He said the danger for the president is that the FBI will indict Manafort "for something irrelevant to the campaign and the Russians and then squeeze him for what he knows that they can use against the president." 
 
 The tough note from Dowd regarding the search warrant is a departure from the tone set in recent days. Dowd earlier this week told USA Today that Trump and Mueller have sent messages “back and forth” and that Trump “appreciates” Mueller’s work. 
 
 A spokesman for Mueller told Fox News that there have been communications among special counsel attorneys and the president’s outside legal team, as well as the president’s special counsel, Ty Cobb. The spokesman told Fox News those communications have been “very professional” and “very cooperative from both sides.” 
 
 Fox News’ John Roberts and Brooke Singman contributed to this report.
– The FBI was listening in on Paul Manafort's conversations long before he became chief of the Trump campaign and it wiretapped him again as part of the investigation of alleged Russian election meddling, source say. The insiders tell CNN that Manafort was initially wiretapped under a secret court order in 2014 in connection with his work as a consultant in Ukraine. That investigation was dropped last year, apparently because there wasn't enough evidence to bring charges, the sources say, but the wiretapping resumed under another secret order which, like the first, was issued under the Foreign Intelligence Surveillance Act. It isn't clear when the second court order was issued, but the warrant extended until at least early this year, long after Manafort parted ways with the Trump campaign, the sources say. They say evidence collected suggests Manafort encouraged the Russians to help the Trump campaign—though the evidence is not conclusive. The New York Times, citing sources including lawyers and witnesses, reports that federal agents, apparently fearing Manafort would destroy evidence, picked a lock and entered without warning when they raided his Virginia home in July. The sources say that after the raid, special counsel Robert Mueller's prosecutor warned Manafort that they planned to indict him. (Mueller has made a move that could be very bad news for Manafort.)