The producer shared what happened with Lauer's co-anchor at the time, Ann Curry, NBC News reported. She told Farrow, "It was as close as you could get to a woman just melting in front of you in pain," according to Fox News.
Lauer said he made a "joking lewd gesture" when asked about what happened but said that he did not expose himself or proposition the woman.
The producer isn't the only woman who had filed complaints about Lauer with NBC.
Originally, network officials said an internal investigation "uncovered no claims or settlements relating to allegations of inappropriate conduct by Matt Lauer that pre-date his firing." Lauer was fired from "Today" in November 2017, NBC News reported.
NBC News Chairman Andrew Lack told staff the managers did not know about Lauer's alleged rape of former producer Brooke Nevils until she filed a formal complaint with human resources.
Lauer has denied he raped Nevils but admitted to sexual encounters with her, but says they were consensual, NBC News reported.
Farrow, however, in the book, says four women signed nondisclosure agreements where the women claimed they were harassed by Lauer and two of the cases were allegedly handled before Lauer's 2017 firing, NBC News reported.
Through his attorney Libby Locke, Lauer said he never exposed himself and, "Ronan Farrow continues his attempt to monetize the MeToo movement, using salacious allegations as promotional trinkets to sell his book. Matt never exposed himself to anyone," NBC News reported.
Locke said the legal team has not received an advanced copy of Farrow's book despite repeated requests, but media outlets have.
"Matt will have more to say at an appropriate time, but he will no longer take part in the marketing circus for this book," Locke added, according to NBC News.
In Farrow's book, which was released Tuesday, he discusses his reporting of Harvey Weinstein's alleged sexual abuse case and the roadblocks he encountered at NBC trying to break the story, USA Today reported.
Farrow ended up writing the Pulitzer Prize-winning investigation for The New Yorker.