(CNN) Kristin Davis, the woman famously known as the "Manhattan Madam," met with special counsel Robert Mueller's team for a voluntary interview on Wednesday, according to four sources familiar with the situation.

Investigators appear to be interested in her ties to longtime Donald Trump adviser Roger Stone, whom she has known for a decade. Sources said investigators expressed interest in having Davis testify before a grand jury -- the latest indication that prosecutors are still aiming to build a case against Stone.

A lawyer for Davis declined to comment. A spokesperson for the special counsel also declined to comment.

Prior to publication of this story, Stone and his lawyer declined to comment. After publication, Stone told CNN in a statement, "Kristin Davis is a long time friend and associate of mine. I am the Godfather to her 2 year-old son. She knows nothing about Russian Collusion, WikiLeaks collaboration or any other impropriety related to the 2016 election which I thought was the subject of this probe. I understand she appeared voluntarily. I am highly confident she will testify truthfully if called upon to do so."

Davis worked with Stone on and off over the years and the two have a close personal relationship.

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