Washington(CNN) Former Trump campaign chairman Paul Manafort's son-in-law, Jeffrey Yohai, met with Department of Justice investigators in recent months, according to two sources familiar with the matter.

Yohai provided information and documents to federal investigators in New York more than two months ago, according to one of the sources.

The sources say the Justice Department was seeking cooperation related to the federal investigation into Manafort for possible money laundering or tax violations in his business dealings with pro-Russia parties in Ukraine.

The information has been turned over to special counsel Robert Mueller as part of his probe. It's unclear if any of the information Yohai provided has been useful for the investigation of Manafort.

Manafort spokesman Jason Maloni declined to comment on this story and an earlier Politico report Thursday that first discussed Yohai being approached about cooperation.

Yohai has been under federal investigation for real estate deals he made with Manafort.

Neither Yohai nor Manafort has been accused of any wrongdoing in either investigation.

An attorney for Yohai declined to comment.

Manafort's daughter, Jessica Manafort, filed for divorce from Yohai in March.

Mueller's team has never requested documents from Manafort, which people close to him say he'd be happy to provide. Last month, Mueller's investigators executed a search warrant at Manafort's Virginia home. A source told CNN the documents seized included financial and tax records and that at least some of the information had already been provided to Senate investigators.

People familiar with the matter tell CNN that Manafort is hiring new lawyers whose expertise is in tax investigations, a signal that Mueller's probe is focusing at least in part on possible tax crimes.

The FBI and the special counsel's office declined to comment.

Republican strategist Roger Stone, a former business partner and longtime friend of Manafort's, said Manafort is "never" going to testify against President Donald Trump.

"Paul is 100% loyal to the President," Stone said on Thursday.

Separately, Mueller's investigation is seeking documents and talking to people regarding former national security adviser Michael Flynn, his lobbying group and work he did on behalf of a Turkish entity, a source familiar with the matter tells CNN. Investigators have been interviewing people associated with Flynn.

Investigators have focused on Flynn's lobbying work for the Turkish government, which he didn't initially disclose as required by law. Flynn's lawyers have since retroactively registered his lobbying.

It was not clear whether Flynn, himself, was asked for documents and interviews.

The request for documents, which was described to CNN, was returned with thousands of pages relating to Flynn and his consulting firm.

Last week, The New York Times reported that investigators asked the White House for documents related to Flynn and have questioned some witnesses about payments Flynn may have gotten from the Turkish government.