The U.S. Olympic Committee has demanded that every member of the USA Gymnastics board resign within six days as part of an overhaul in response to the Larry Nassar sex abuse scandal.

Calling for a “categorically fresh start,” USOC officials threatened to decertify the national governing body if it does not satisfy a series of swift reforms.

“We do not base these requirements on any knowledge that any individual USAG staff or board members had a role in fostering or obscuring Nassar’s actions,” USOC Chief Executive Scott Blackmun wrote. “Our position comes from a clear sense that USAG culture needs a fundamental rebuilding.”

The demands were included in a letter sent to the gymnastics organization’s Indianapolis headquarters on Thursday, shortly after Nassar was sentenced to up to 175 years in prison for molesting young athletes.

Scores of women — including Olympic champions such as Gabby Douglas, Aly Raisman and McKayla Maroney — have said Nassar sexually abused them while he was serving in an official capacity for USA Gymnastics, Michigan State University and other organizations.

The former Olympic team doctor was sentenced to 60 years on child pornography charges.

Fallout from the scandal has already prompted the suspension of Olympic coach John Geddert and the resignation of three key USA Gymnastics board members. Lou Anna Simon, the president of Michigan State, also stepped down on Thursday.

USA Gymnastics vowed to adhere to the latest USOC demands.

“We understand that the requirements imposed by the letter will help us enhance our ability to build a culture of empowerment throughout the organization, with an increased focus on athlete safety and wellbeing,” the national governing body said.

The USOC has asked that an interim board be established by the end of February and that permanent replacements be found within 12 months. It also seeks to have a designated liaison present at all future board meetings.

USA Gymnastics has been ordered to cooperate with an independent investigation commissioned by the USOC to determine when complaints were first brought against Nassar and why his actions went unaddressed over the course of decades.

“Please understand that the circumstances that led to this crisis demand our attention and intervention,” Blackmun wrote in the letter. “Our common focus and motivation needs to be athlete support and protection.”