The CEO and publisher of the Los Angeles Times is on an unpaid leave while under investigation by the paper's parent company, Tronc, following an NPR report about what it said was "questionable behavior" in his past.

Ross Levinsohn "has voluntarily agreed to take an unpaid leave of absence, effective immediately," Tronc CEO Justin Dearborn said in a message to employees Friday afternoon. "The company has retained Sidley Austin LLP to conduct a review of the allegations regarding his behavior."

Times president Mickie Rosen "will lead the Los Angeles Times" in Levinsohn's absence, Dearborn said. The paper's editor-in-chief, Lewis D'Vorkin, will continue leading the newsroom.

Levinsohn has not responded to requests for comment about the allegations.

Prior to Dearborn's announcement, the Times newsroom had been speaking up loudly against Levinsohn. More than 180 newsroom staffers had signed a letter to Tronc's board calling for Levinsohn's removal.

"Levinsohn has lost credibility as the leader of one of the country's top newspapers. He has to go -- without a cent more of company money," the letter, a copy of which was obtained by CNN, said.

Two sources in the Times newsroom said the letter would formally be sent to the board on Friday.

The letter is the latest sign that the newsroom is in a state of revolt against Tronc. On Friday, a tally by the National Labor Relations Board revealed that newsroom employees had voted to form a union, a historic first for the paper, which had long been staunchly anti-union.

This latest controversy erupted after NPR's David Folkenflik reported on Thursday afternoon that Levinsohn "has been a defendant in two sexual harassment lawsuits and that his conduct in work settings over the past two decades has been called into question repeatedly by female colleagues."

CNN has confirmed through court records that those two lawsuits were, in fact, filed.

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Levinsohn was put in charge of the paper just five months ago. He was previously a senior executive at Yahoo and Fox Interactive Media.

Folkenflik said he conducted 26 interviews and reviewed court documents, among other things. What he found, he said, suggests "a pattern of questionable behavior and questionable decisions on the job. The portrait that repeatedly emerges is one of a frat-boy executive, catapulting ever higher, even as he creates corporate climates that alienated some of the people who worked for and with him."

Veterans of the newspaper say they are deeply concerned. On Thursday evening a dozen of the Times' senior editors -- representing most of the paper's leadership -- sent a letter to Tronc's board of directors stating that the alleged behavior "jeopardizes The Times' 136-year legacy of integrity."

The editors also said they are aware of "additional, credible reports" of misconduct.

At the same time, the broader letter from staffers gained dozens and dozens of signatures. As of Friday morning, more than 180 reporters, editors and other staffers had signed it, according to three newsroom sources.

After NPR's story came out, Tronc said in a statement that it was not aware of the allegations until recently.

"This week, we became aware of allegations that Ross Levinsohn acted inappropriately," the company said. "We are immediately launching an investigation so that we have a better understanding of what's occurred."

"At Tronc," the statement added, "we expect all employees to act in a way that supports a culture of diversity and inclusion. We will take appropriate action to address any behavior that falls short of these expectations."

A spokeswoman for the company said she could not comment further on Levinsohn's status or the Tronc board of director's plans.

Levinsohn, the latest in a series of business-side bosses at the Times, has faced resistance from newsroom staffers in his first months on the job.