Top executives at NBC News learned that two news outlets were working on articles about sexual misconduct involving Matt Lauer several weeks before a female worker came forward with the accusations that led to the firing of the longtime “Today” anchor, the network said Friday.

But the network could not find any evidence of complaints against Lauer, or settlements that might have been reached. And when executives asked Lauer directly if there ever was any sexual misconduct, Lauer denied it, saying he was “racking his brain and couldn’t think of anything at all,” one executive said.

The executives who questioned Lauer included NBC News President Noah Oppenheim and NBC News Chairman Andy Lack.

The statement from the network's senior management came as NBC News launched a review into the events that ended with Lauer’s dismissal on Wednesday. The network also flatly denied that Lauer would receive any kind of monetary settlement. Lauer was fired “for cause” and there will be no final payout, one executive said.

On Friday, Lack sent a letter to the NBC News staff to assure them the network was investigating the events surrounding Lauer's firing and taking steps to prevent further sexual harassment.

“A team of the most experienced NBC Universal Legal and Human Resources leaders have begun a thorough and timely review of what happened and what we can do to build a culture of greater transparency, openness and respect for each other,” Lack said. “At the conclusion of the review we will share what we’ve learned, no matter how painful, and act on it.”

Lack’s letter arrived days after NBC News stunned the media world by firing Lauer, the longtime anchor of “Today,” following a detailed complaint from a female colleague who accused him of inappropriate sexual behavior during the 2014 Sochi Olympics. The conduct continued after the games ended, she said.

“Many of you have asked what we are doing to learn as much as we can about the circumstances around Matt Lauer’s appalling behavior, why this was able to happen, and it wasn’t reported sooner,” Lack wrote. “This week we saw that when an employee comes forward to report misconduct, the system works.”

But, Lack added, “we also learned that we must do a much better job of making people feel empowered to take that crucial first step of reporting bad behavior.”

NBC News already requires workers to do online sexual harassment training, but in the wake of Lauer’s ouster Lack said they are beefing up the process with “in-person training” on “appropriate behavior in the workplace.”

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Lack also encouraged employees to “speak up and raise any concerns you have about inappropriate conduct you have experienced or observed” and urged managers to do so as well.

Lauer, 59, issued a statement that was read Thursday on the show he anchored for two decades, in which he said he was “truly sorry.”

“Some of what is being said about me is untrue or mischaracterized, but there is enough truth in these stories to make me feel embarrassed and ashamed,” he wrote.

Lauer's statement did not go into detail. But in addition to the complaint that got him fired, The New York Times reported that two women also came forward after he was fired to accuse him of misconduct, including one who claims he sexually assaulted her in his office in 2001.

NBC officials later confirmed that two more accusers came forward on Wednesday.

Also, Variety published an article following a two-month investigation that portrayed Lauer as a serial harasser who preyed on the female producers who worked on “Today.” The article said several women reported the incidents, but that their complaints fell on deaf ears.

None of the accusers in the story were named and NBC has not yet confirmed their accounts.

NBC officials denied that anyone now in management knew about Lauer's actions. "We can say unequivocally, that, prior to Monday night, current NBC News management was never made aware of any complaints about Matt Lauer’s conduct," a spokeswoman said.

Excerpts from Lack's letter are below:

Dear Colleagues,

The most vital thing we’ve done since terminating Matt Lauer’s employment on Tuesday night has been spending time listening to your concerns, your feedback, your ideas on how we move forward as an organization.

As I said in my note on Wednesday: our highest priority is to create a workplace environment where everyone feels safe and protected, and to ensure that any actions that run counter to our core values are met with consequences, no matter who the offender.

Many of you have asked what we are doing to learn as much as we can about the circumstances around Matt Lauer's appalling behavior, why this was able to happen, and why it wasn’t reported sooner.

This week we saw that when an employee comes forward to report misconduct, the system works. The complaint is quickly assessed and meaningful action is taken. But we also learned that we must do a much better job of making people feel empowered to take that crucial first step of reporting bad behavior.

To that end, I have three things to share with you.

A team of the most experienced NBCUniversal Legal and Human Resources leaders have begun a thorough and timely review of what happened and what we can do to build a culture of greater transparency, openness and respect for each other. At the conclusion of the review we will share what we’ve learned, no matter how painful, and act on it.

Second – while our company has had mandatory online training for all employees on sexual harassment and other workplace issues, we need to do better. Therefore in addition to what is already in place, the News Division is launching an immediate effort to implement in-person training on sexual harassment awareness and appropriate behavior in the workplace. We will share more details on this effort very shortly.

And third— we need to keep communicating. In addition to the meetings we’ve had this week with various show teams and departments, we are encouraging the leaders of every group to have smaller, more informal gatherings to further discuss this crucial issue now and on an ongoing basis.

And, as we have done regularly over the last few months, but cannot do often enough, we want to remind you again that we encourage all employees to speak up and raise any concerns you have about inappropriate conduct you have experienced or observed. We also want to reinforce with our managers and leaders their responsibility to bring forward concerns about inappropriate workplace behavior they see or hear about. It is always the right thing to do, and any concerns raised should be done without fear of retaliation, and with full assurance that they will be investigated.

This has been a very tough week for all of us. Thank you again for your honest feedback. I’ll continue to share information and updates with you in the days and weeks ahead.

Andy