CHICAGO -- Michigan State University, already reeling from the scandal involving a gymnastics doctor who molested young athletes, has maintained ties to a prominent volleyball coach for decades after he was publicly accused in 1995 of sexually abusing and raping six underage girls he trained in the 1980s.

Letters obtained by The Associated Press from advocates for the accusers reveal the school has been under pressure for at least a year to sever its relationship with Rick Butler. He runs training facilities in suburban Chicago that for decades have been a pipeline for top volleyball recruits, including Michigan State. MSU also held exhibition games for successive years at his facilities, at least through 2014, according to online records.

Butler's accusers say Butler threatened to use his national influence to thwart their college prospects if they didn't accept his advances.

Questions about ties to Butler add to the scrutiny of Michigan State that began when Dr. Larry Nassar was charged in 2016 with abusing scores of gymnasts over 20 years while he had an office on campus. A former dean, William Strampel, was recently charged with failing to protect patients from Nassar and with sexually harassing female students.

Unlike Nassar, who will spend the rest of his life in prison, the 63-year-old Butler has never been criminally charged and has denied sexually abusing anyone. The conduct in question occurred more than 30 years ago and was already beyond the statute of limitations for prosecution when the first three accusers came forward in 1995. Three others came forward more recently.

One of the initial accusers, Sarah Powers-Barnhard, said Butler molested her hundreds of times over two years starting when she was 16 and he was around 30. She says he raped her at his home, in cars and even in a train-car bathroom as her teammates sat nearby.

Michigan State has "turned a blind eye" to Butler's sordid history, she said.

"If we don't stop supporting the top abuser in volleyball, how can we ever claim zero tolerance for sexual abuse?" she said from her Jacksonville, Florida, home.

In a short Monday statement responding to AP questions about Butler's connections to Michigan State and its head women's volleyball coach, MSU said Butler is currently "not affiliated with MSU in any way." The university, it added, "is not actively recruiting players from his program at this time."

But the eight-sentence statement did not address other questions put to it by the AP, including how long the school has been aware of the allegations, when any affiliation with Butler might have ended or why MSU had ties to him for so long after he was publicly accused of sexual abuse and rape.

In a 1995 report, the Illinois Department of Children and Family Services found no evidence to support Butler's contention that the three athletes were lying.

Butler acknowledged during a 1995 hearing held by USA Volleyball, the sport's national governing body, that he had sex with the three. He insisted it was after they turned 18 and was consensual. He has described the allegations as a "smear campaign."

USA Volleyball in December banned Butler from its events for life, and the Amateur Athletic Union stripped him of his membership early this year. Those groups acted under pressure from some of the same activists now pressing Michigan State about Butler.

Many college coaches are reluctant to criticize the onetime Olympic team trainer. That's true, in part, because he consistently produces stellar recruits via his flagship company, Sports Performance Volleyball, and his 12-court Great Lakes Center. Both of them are in Aurora, west of Chicago. Each year, he holds what many colleges consider can't-miss recruiting events where his players are showcased.

"Coaches are afraid that if they don't show deference to Butler, he'll steer recruits to other schools," said Kay Rogness, who in the '80s helped establish Sports Performance. She fell out with Butler around 1990 and has since become one of his harshest critics.

Among the many coaches who worked early in their careers for Sports Performance was Michigan State head volleyball coach Cathy George. Since becoming coach in 2005, most of her teams have featured one or more players trained by Butler. Michigan State's website mentions Butler by name, citing athletes trained by him.

Powers-Barnhard said George called her after the allegations emerged in 1995. She knew Powers-Barnhard from when they played against each other. George expressed sympathy but said she could not refuse to deal with Butler, according to Powers-Barnhard.

At the time, George was head coach at Western Michigan University. "She said, 'I'm sorry all this happened, but I will still have to recruit from him,"' said Powers-Barnhard, a three-time All American.

There was no response to email and voice messages left for George on Monday.

Michigan State cannot plausibly claim it was unaware of the allegations.

Chicago-area media widely covered the accusations when the first accusers came forward in 1995. The allegations have been covered periodically since then, including in a 2015 feature on the ESPN's "Outside the Lines" and in a recent Chicago Sun-Times series.

Efforts to banish Butler have been driven partly by Nancy Hogshead-Makar, an Olympic swimming champion who later became a civil rights lawyer. She now leads a Florida-based group called Champion Women, which advocates for female athletes.

The school's volleyball coach "is conducting business with ... a known sexual abuser," Hogshead-Makar wrote on July 21, 2017 , to then-Michigan State athletic director Mark Hollis and to the school's then-general counsel, Robert Noto. She got no response.

She also attached a photo of George sitting with Butler at a girls' national volleyball tournament in Florida last year, when multiple players for other teams wore T-shirts citing allegations against Butler. The photo was from a report by Jacksonville's First Coast News television.

In a Jan. 19 letter , Hogshead-Makar said the university had obligations to avoid dealing with Butler under Title IX, the federal law forbidding sex discrimination in education. Michigan State did not respond.

"Therefore, it is not only your moral, but also your legal duty to make sure that Rick Butler is unable to harm more athletes," she wrote in the note to then-MSU President Lou Anna Simon and Jessica Norris, the school's director of Title IX efforts.

In response to a similar email last year from part-time volleyball coach and activist Chris Murdock, associate athletic director Shelley Appelbaum said issues surrounding Butler were "still unfolding" and that the university would "monitor the situation."

Butler sounded confident in a statement to PrepVolleyball.com after the Amateur Athletic Union cancelled his membership, saying he emailed 600 families about the AAU action and that no families pulled kids from his programs. Those programs, he added, "will not miss a beat."

There was no response to Monday voice and email messages left for Butler.

The bans on Butler do not prohibit him from training children, said Emily Swanson, a Denver lawyer who has also spoken out against him. She said his staying power derives from coaches who keep going to him for recruits. She urged schools to refuse to recruit his athletes, even if some miss out on scholarships as a result.

"If schools stopped recruiting his players, players would stop going to him to train," she said. "That would shut him down."