COLORADO SPRINGS, Colo. -- Saying the Olympic family had utterly failed to protect its own, the chief executive officer of the U.S. Olympic Committee, Scott Blackmun, announced an independent investigation Wednesday intended to determine how the sexual abuse attributed to former USA Gymnastics sports doctor Larry Nassar could have gone on as long as it did.

In what he called an open letter to Team USA, Blackmun said the third-party investigation will attempt to determine "who knew what and when" when it comes to Nassar, who was sentenced Wednesday to 40 to 175 years in prison for molesting seven women. Blackmun did not identify who would do the investigation or how long it would take, but he said the results will be made public.

Olympians Aly Raisman, McKayla Maroney, Jordyn Wieber and Simone Biles were among more than 100 gymnasts who say they were abused by Nassar over the years. Many victims said there were others to blame for enabling Nassar, from his employers at Michigan State University to USA Gymnastics and beyond. They laid out in searing and heart-wrenching detail the abuse and the lack of support they felt during a seven-day hearing in Michigan that culminated with Nassar's sentencing.

"The athlete testimony that just concluded in the Nassar hearings framed the tragedy through the eyes of the victims and survivors, and was worse than our own worst fears," Blackmun said. "The USOC should have been there to hear it in person, and I am deeply sorry that did not happen. The purpose of this message is to tell all of Nassar's victims and survivors, directly, how incredibly sorry we are. We have said it in other contexts, but we have not been direct enough with you. We are sorry for the pain caused by this terrible man, and sorry that you weren't afforded a safe opportunity to pursue your sports dreams. The Olympic family is among those that have failed you."

Nearly a year ago, USA Gymnastics president Steve Penny resigned under pressure from the USOC. Penny joined USA Gymnastics in 1999 and oversaw one of the greatest runs in Olympic history, success that made the federation a magnet for big-time corporate sponsors who wanted to be aligned with its healthy, winning image.

That image took a major blow after an investigation by the Indianapolis Star portrayed USA Gymnastics as slow to act when it came to addressing allegations of sexual abuse. Some sponsors have left, and last fall, Jamie Dantzscher, a member of the 2000 Olympic team, filed a civil lawsuit in California against USA Gymnastics and Nassar. Other lawsuits have followed, including some that name Penny, Martha Karolyi and her husband, Bela, as co-defendants because they allegedly knew about Nassar's abuse.

Martha Karolyi retired in August 2016. A short time later, USA Gymnastics hired a former federal prosecutor, Deborah Daniels, to conduct an extensive review of the organization's policies in regard to potential sexual misconduct. She concluded that the organization's culture emphasized performance over protection.

Blackmun said the immediate goals now are to change that culture, revise the governance structure of federations like USA Gymnastics and devote time and resources to helping abuse victims and survivors.

He noted that the USOC has been in talks with USAG since October and that new leadership was critical. In the past week, three USAG board members have resigned and the Indianapolis-based organization severed ties with the Karolyi Ranch in Texas, a longtime training site where many survivors said they were abused.

Blackmun said those steps were not enough and called for a "full turnover of leadership," including all current USAG directors.

The USOC considered decertifying USA Gymnastics as a national governing body for the sport, Blackmun said, but that would harm clubs and athletes that had nothing to do with the Nassar scandal. He said decertification will remain a possibility.

In response, USA Gymnastics issued a statement supporting the investigation and accepting "the absolute need of the Olympic family to promote a safe environment for all of our athletes." It did not refer to Blackmun's call for more resignations.

"We agree with the USOC's statement that the interests of our athletes and clubs, and their sport, may be better served by moving forward with meaningful change within our organization, rather than decertification," the organization said. "USA Gymnastics supports an independent investigation that may shine light on how abuse of the proportion described so courageously by the survivors of Larry Nassar could have gone undetected for so long and embraces any necessary and appropriate changes."

The U.S. Olympians and Paralympians Association released its own letter to athletes that praised survivors for coming forward.

"We are both appalled by the actions of those who hurt you and deeply saddened by your suffering," the letter read. "For those whose stories we haven't heard (and may never hear), we respect your decision and your privacy but also acknowledge the pain you feel in silence."