"We have been failed and we deserve answers," Biles has told a Senate Judiciary Committee.
The 24-year-old made the shock decision on Wednesday to withdraw from the team gymnastics finals.
The American became the first woman to attempt and complete the mind-blowing vault at the US Classic.
A former Olympian says the future of the sport is much brighter.
The investigation followed complaints about the mistreatment of gymnasts.
"There is a long history of research into maltreatment in artistic gymnastics."
Former WADA boss David Howman has been appointed to lead the investigation.
A toxic, bully-ridden environment within the sport has been reported in recent days.
One athlete was told to keep training despite sustaining a head injury during practice.