Simone Biles, McKayla Maroney, Maggie Nichols and Aly Raisman - four gymnasts known for their accolades - joined abuse survivors at Capitol Hill Wednesday as the Senate Judiciary Committee investigates the FBI's mishandling of disgraced U.S. gymnastics team doctor Larry Nassar's sexual abuse case.

Connecticut's Sen. Richard Blumenthal was among those questioning the U.S. Olympic stars. Inspector General Michael Horowitz testified that FBI agents later lied to investigators as part of a failed cover-up.

"To be clear, I blame Larry Nassar, but I also blame an entire system that enabled and perpetrated his abuse," says Biles.

Maroney says after she first came forward in 2015, law enforcement allowed Nasser to molest dozens of other victims.

"They chose to lie about what I said and protect a serial child molester rather than protect, not only me, but countless others," says Maroney.

FBI Director Christopher Wray also testified that the bureau has already begun strengthening its training and procedures.

The FBI announced Wednesday morning that it has fired Michael Langeman, one of the lead agents charged with failing to open a criminal investigation into Nassar's abuse.

Biles is on the cover of Time Magazine as one of the 100 most influential people in the world.