NBC News announced Friday that it would require harassment-prevention training for all its employees and would conduct a "culture assessment" of the news division.

NBC News Chairman Andy Lack, in a memo to the staff, also said that a review of the sexual harassment charges that led to the firing of "Today" anchor Matt Lauer would result in interviews with at least 40 employees. The review, he wrote, is intended "to determine why this was able to happen, why it wasn’t reported sooner, and what we can do to make employees feel more empowered to report unacceptable behavior."

Lauer was fired last week for "inappropriate workplace behavior," after a woman told NBC officials about his misconduct. Subsequent news reports included accusations from multiple women who described Lauer as a sexual predator over several years, and suggested that NBC executives had received complaints about his behavior at the time. NBC issued a statement saying that no current members of the network's management were aware of Lauer's actions.

Lack said the culture assessment would bring together peer groups of up to 10 employees to discuss what might prevent staff members from coming forward with their concerns, and how employees feel about their work environment.

"The assessment will also look at the questions, did the culture here change over time, and if so how?" he wrote.

To "cut this problem off at its roots," Lack wrote, NBC has hired an outside firm to conduct "in-person, interactive training on workplace behavior and harassment prevention." The name of the firm was not disclosed in the memo, and an NBC spokesperson declined to comment further on the note.

"I’m grateful as ever to all of you for your professionalism and focus during difficult days," he wrote. "No doubt there is more hard work to be done, but we will do it together."