The FBI's probe into serial sex abuser Larry Nassar was beginning to face scrutiny Monday, even as the disgraced former USA Gymnastics doctor was sentenced to a third prison term -- this time for up to 125 years -- for molesting hundreds of young girls at an elite training center.

In the case for which he was sentenced Monday, Nassar, 54, pleaded guilty to penetrating girls with ungloved hands when they sought treatment for injuries at Twistars, a Michigan gymnastics club that was run by a 2012 U.S. Olympic coach.

More than 260 women and girls have said they were assaulted by Nassar, with some accusations dating as far back as the 1990s. Most victims who wanted to speak publicly or submit a statement did so earlier, during Nassar's seven-day court hearing in Ingham County -- including 2012 Olympic teammates Aly Raisman, Jordyn Wieber and McKayla Maroney. In that case, he was sentenced to 40 to 175 years in prison in another county and to a 60-year federal term for child pornography crimes. He worked for Michigan State and USA Gymnastics, which trains Olympians.

Monday's sentence comes amid questions about the speed of the federal probe into the Nassar allegations.

From the time when Nassar first began to be investigated by the FBI in July 2015 to when he was publically named in a blockbuster investigation by the Indianapolis Star in September 2016, at least 40 girls and woman are known to have been molested, according to an analysis by the New York Times.

Three of the victims that were part of the agency's investigation were world-class athletes, including two Olympic gold medalists -- but it took nearly a year before they were interviewed by FBI agents, according to The Times.

MICHIGAN COPS TO APOLOGIZE FOR BELIEVING LARRY NASSAR OVER 17-YEAR-OLD VICTIM

“I never got a phone call from the police or the F.B.I.” Gina Nichols, mother of gymnast Maggie Nichols, told the New York Times. “Not one person. Not one. Not one. Not one.”

The FBI declined to answer detailed questions from the newspaper on its investigation, instead saying in a statement "the safety and well-being of our youth is a top priority for the F.B.I.," and the scope of the Nassar investigation “transcended jurisdictions."

The Nassar scandal also rocked Michigan State, which has been accused of repeatedly missing opportunities to stop Nassar. The doctor had a campus office and was a revered figure in sports medicine.

Lou Anna Simon resigned as Michigan State's president on Jan. 24 and athletic director Mark Hollis followed two days later. The longtime leader of USA Gymnastics, Steve Penny, quit last March, and all board members recently stepped down at the demand of the U.S. Olympic Committee.

A law firm has been hired to investigate how the USOC responded to its knowledge of allegations against Nassar.

DAD WHO CHARGED AT LARRY NASSAR RECEIVING HUNDREDS OF DONATIONS

The trial has also caused deep emotions to play out in the courtroom among the victims and their families. On Friday, Nassar was almost attacked by a man whose three daughters said they were abused.

Randy Margraves was tackled by sheriff's deputies Friday before he could pummel Nassar. He said he wanted just a minute in a locked room with the "demon."

"This cannot be a lawless society. I know that," Margraves, 58, told reporters during a public apology. "I lost control, but I gained control later in a holding cell."

The Associated Press contributed to this report.