Olympic gymnast Simone Biles said she was pained to learn that she was left out of USA Gymnastics' initial investigation of former team doctor and convicted pedophile Larry Nassar.

Biles, a gold medalist who is widely considered the top gymnast in the world, was one of several athletes who expressed concerns about Nassar to USA Gymnastics officials in June 2015, according to notes collected in a U.S. Senate investigation. USA Gymnastics hired someone in July 2015 to speak to several national team gymnasts about their concerns and subsequently passed that information on to the FBI, which opened its own investigation into Nassar. Biles wasn't informed about either investigation until more than a year later. The Wall Street Journal reported this week that Biles learned of the investigations only after returning from her gold-medal performance at the 2016 Olympic Games.

"Can't tell you how this is to read and process," Biles tweeted in response to the Wall Street Journal story. "The pain is real and doesn't just go away... especially when new facts are still coming out. What's it going to take for a complete and independent investigation of both USOPC and USAG???"

Biles has previously expressed frustration and sadness with how she and other survivors of sexual assault have been treated by USA Gymnastics as she continues to work toward another Olympic appearance in Tokyo this summer. She said Thursday on social media that "numb is becoming a normal feeling."

Biles' concerns about Nassar came up in email conversations between former USAG president Steve Penny and women's national team director Rhonda Faehn during the summer of 2015. Penny said in that exchange that he would set up a meeting between Biles and private investigator Fran Sepler, but the meeting never happened.

Penny told The Wall Street Journal, through his attorney, that he was aware in July 2015 that Biles was one of the gymnasts that USAG "might want to talk to about Nassar." Penny failed to mention Biles' name when he reported Nassar to the FBI that summer. Penny resigned from USA Gymnastics in March 2017 amid the fallout from Nassar's crimes. He was charged with tampering with evidence related to Nassar in October 2018 and has pleaded not guilty.

Nassar resigned from his role with USA Gymnastics in September 2015, but continued to see gymnasts and patients through his work at Michigan State University for another year. Nassar said he was retiring to spend more time with his family. USA Gymnastics did not refute his story or notify Michigan State that the FBI was investigating the doctor based on information that Penny had shared with them.

The FBI interviewed Olympian McKayla Maroney about Nassar on the phone in September 2015, then waited months before following up or contacting other national team members who were interviewed as part of USAG's internal investigation. A U.S. Senate report criticized the FBI for an investigation that "dragged on and was shuffled between field offices" while Nassar continued to see patients for more than a year. Dozens of young women and girls say they were sexually assaulted by Nassar during the 13 months between the FBI learning of complaints about Nassar and when he was fired from Michigan State in the wake of public accusations about his sexual abuse.

The Department of Justice's Office of Inspector General started its own investigation in 2018 to review the FBI's handling of the Nassar case. No results of that review have been made public yet.

A group of Olympic gymnasts, including Maroney and Aly Raisman, called on the Justice Department in an article published this week in The Orange County Register to share its findings. Maroney told the California newspaper that she and others were "tired of waiting."

"Though progress has been made, so much truth has not yet seen the light of day," she wrote in an email. "Justice for myself and all my fellow gymnasts won't be served until that day arrives."