GRAND RAPIDS, Mich. -- Eighteen current and former female athletes have filed a lawsuit in U.S. District Court claiming that Larry Nassar, the former USA Gymnastics and Michigan State University doctor, sexually abused them during medical exams.

The lawsuit is the latest in a series of court cases targeting Nassar. More than 65 women have filed lawsuits or police complaints of sexual assault against him, including former U.S. gymnastics national team members. He also faces criminal charges for sexual abuse and child pornography.

The accusers in the new lawsuit ranged in age from 9 to 29 years old at the time of the abuse, according to a civil complaint filed Tuesday morning in Michigan.

Nassar, 53, is perhaps best known for his work with the U.S. women's gymnastics team. He started working international competitions with America's elite gymnasts as a trainer in 1986 and as team doctor in 1996.

Nassar was dismissed by USA Gymnastics in the summer of 2015 after gymnasts told officials with the sport's governing body about his alleged behavior during medical exams, but he continued to treat patients in and around Lansing, Michigan, for more than a year thereafter even though his conduct was, at the time, under the scrutiny of the FBI.

The plaintiffs who filed suit Tuesday participated in a variety of sports, including gymnastics, swimming, figure skating, track and field, field hockey, basketball and soccer.

Some were treated at Nassar's campus office within the Michigan State sports medicine facility, and others were treated at Twistars Gym, a gymnastics training center near Lansing where Nassar also saw patients.

In addition to Nassar, Michigan State University, Twistars and USA Gymnastics are all named as defendants in the lawsuit, which says that all three institutions should have stopped Nassar's alleged behavior years before they finally severed ties with him.

"We intend to show and prove that the young women we represent were betrayed not only by a doctor that used his reputation and position of trust to commit sexual abuse and assaults upon their bodies for his own gratification," says Stephen Drew, one of the plaintiffs' attorneys, "but that the institutions and those in them with a responsibility to protect those children and young women failed to do so."

Nassar and Twistars could not be reached immediately for comment. In the past, Nassar has denied claims of abuse, saying that he was performing a standard medical procedure.

In a statement, Michigan State spokesman Jason Cody said, "While we cannot comment specifically on pending or ongoing litigation, we are deeply disturbed by the state and federal criminal charges against Larry Nassar, and our hearts go out to those directly affected. The criminal investigation into Larry Nassar is a top priority for MSU Police. Detectives are vigorously reviewing all complaints and working through them with the state Attorney General's office and federal U.S. Attorney's Office."

According to the statement, Michigan State began an internal review of Nassar's work for the university in September. It cited one 2014 complaint that "was investigated by MSU Police and our Title IX office," but beyond that, the statement said, "To date, MSU's review has discovered no evidence that any individuals came forward to MSU with complaints about Nassar before Aug. 29, 2016."

USA Gymnastics also issued a statement: "USA Gymnastics finds the allegations against Dr. Nassar very disturbing. When we first learned of athlete concerns regarding Dr. Nassar in the summer of 2015, we immediately notified the FBI and relieved him of any further assignments. USA Gymnastics has fully cooperated with the FBI in its investigation. We find it appalling that anyone would exploit a young athlete or child in this manner, and we are grateful to the athletes who have come forward."

The alleged abuse dates back as far as 1996, according to the lawsuit. The plaintiffs all make highly similar claims, saying that Nassar, "under the guise of treatment," inserted his ungloved fingers into their vaginas and/or rectums and, in some cases, groped their breasts.

Some of the victims, minors at the time, had gone to see Nassar for injuries to their hamstrings and elbows.

Rachael Denhollander, the lead plaintiff in the lawsuit and the only one named, alleges that Nassar sexually abused her during a medical exam in 2000, when Denhollander was a 15-year-old club-level gymnast.

"On approximately five separate occasions, at appointments at his office at MSU, Defendant Nassar digitally penetrated Plaintiff Denhollander's vagina and anus with his finger and thumb without prior notice and without gloves or lubricant under the guise of performing 'treatment,'" the lawsuit states.

Denhollander didn't report Nassar to Michigan State University Police until August 2016. Her police report, first made public by The Indianapolis Star, led to dozens of accusations from other women, many of them athletes. More than 60 other women have since filed similar complaints against Nassar with Michigan State University Police.

Warning signs about Nassar's behavior during medical exams were raised years earlier.

Last month, Tiffany Lopez, a former Spartans softball player, filed a lawsuit against Nassar in Los Angeles County Superior Court.

In 1997, Lopez, known then by her maiden name, Tiffany Thomas, was a softball player on full scholarship, a freshman who helped lead the Spartans to the NCAA regional tournament for only the second time in school history. After she developed chronic lower-back pain in 1998, university athletic trainers sent her to see Dr. Nassar.

Lopez alleges that Nassar sexually abused her during medical exams over a period of three years.

When she grew disturbed by his methods and complained to the training staff, Lopez says she was told that Nassar was a world-renowned doctor and that his treatments, which he called "inter-vaginal adjustments," were legitimate practice.

Lopez's lawsuit is among a mounting list of civil and criminal complaints against Nassar:

In early September, a former gymnast on the U.S. women's national team, a 2000 Olympic medalist, sued Nassar and the sport's governing body, USA Gymnastics, claiming that Nassar assaulted her when she traveled for competitions. Nassar penetrated the plaintiff in her sleeping quarters while she wasn't supervised by a chaperone, according to the lawsuit. During one exam, he allegedly talked about oral sex.

In late October, a second former gymnast with the U.S. women's national team filed suit against Nassar, claiming that he sexually assaulted her during medical exams and that the legendary former coaches, Bela and Marta Karolyi, failed to protect her and engaged in their own pattern of physical and emotional abuse. The suit also claims that top USA Gymnastics officials had "wide-ranging knowledge" of the abuse but for years "concealed and ignored" it.

Last month Nassar was charged with three counts of first-degree criminal sexual conduct with a person under 13. The charges, announced by Michigan Attorney General Bill Schuette, do not involve an athlete but rather a girl Nassar allegedly sexually assaulted in his home in Holt, Michigan, between 1998 and 2005.

Also last month, Nassar was arrested on two counts of possessing and receiving child pornography. According to U.S. Attorney Patrick Miles, Nassar had 37,000 images on his computer, including images of a girl younger than 12.

Nassar has remained in jail since his arrest last month on child pornography charges.

John Barr is a reporter for ESPN's Enterprise Unit. He can be reached at John.A.Barr@espn.com. Follow him @JohnBarrESPN. Nicole Noren is a producer in ESPN's Enterprise Unit. She can be reached at Nicole.K.Noren@espn.com.