Former Trump campaign chairman Paul Manafort was wiretapped by U.S. government investigators both before and after the 2016 presidential election, according to a report out Monday night.

The wiretapping was authorized by a secret Foreign Intelligence Surveillance Act (FISA) court after the FBI started to investigate Manafort, 68, in 2014, CNN reported. He's been under scrutiny over his financial dealings and lobbying efforts with pro-Russia and Ukrainian officials but has denied colluding with Russia to influence the election.

The order to monitor Manafort was discontinued in 2016, but investigators obtained another FISA warrant that stretched into early 2017, according to the report.

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Some of the intelligence collected during the surveillance reportedly signaled that Manafort may have pushed for Russian officials to help try to get then-candidate Donald Trump elected. However, sources told CNN the evidence was not conclusive.

Manafort, according to the report, was not surveilled during the June 2016 Trump Tower meeting in which Donald Trump Jr., Jared Kushner and Manafort met with Kremlin-linked attorney Natalia Veselnitskaya.

Manafort – who is a key figure in Special Counsel Robert Mueller’s investigation into Russia’s involvement with the election – had his Virginia home raided in July by FBI agents who were looking for financial documents related to the election.

The FBI took documents and other materials related to Mueller’s investigation during the raid, just one day after Manafort had voluntarily met with members of the Senate Intelligence Committee.

The raid was followed up with a warning to Manafort from Mueller’s prosecutors that they planned to indict him, The New York Times reported.

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Manafort, a longtime GOP operative who worked for former Presidents Ronald Reagan and George H. W. Bush, stepped down as the Trump campaign’s chairman in August 2016 amid mounting speculation surrounding his ties to Ukrainian politics.

Warrants of this nature are difficult to come by, as the FISA court and its orders are highly secretive. Judges grant permission to surveil people they think may be working as an agent of a foreign power.

If the CNN report is confirmed, Manafort would be the second person affiliated with the Trump campaign known to be monitored under a FISA warrant, behind former campaign adviser Carter Page.

Manafort, who registered as a foreign agent this summer, has said his work in Ukraine was not related to the 2016 campaign.