Authorities are investigating Karolyi Ranch, the U.S. Olympic training facility in Texas where some gymnasts have said former team doctor Larry Nassar sexually abused them.

The Walker County Sheriff's Office confirmed that the office has an open investigation into the ranch outside Huntsville, but would not say what the investigation is about or when it began.

A message left on the ranch's voicemail wasn't returned.

Karolyi Ranch was formerly run by national team coordinator Martha Karolyi and her husband, Bela, and it previously served as the National Training Center for the Women's National Team. A 2016 lawsuit filed in California accuses the Karolyis of being physically abusive to athletes and turning a blind eye to Nassar's alleged abuse.

On Thursday, USA Gymnastics announced it was ending its relationship with the ranch, which will no longer serve as the National Training Center. The organization also cancelled a training camp at the ranch that was set to be held this week.

In the absence of a training facility, Valeri Liukin, the current head coach of the Women's National Team and father of gymnast Nastia Liukin, has offered up one of his two gyms in Plano and Frisco as a temporary home.

On Monday, three members of the organization's board of directors — chairman Paul Parilla, vice chairman Jay Binder and treasurer Bitsy Kelley — resigned.

That decision came days after Olympic gold medalist Simone Biles, who grew up outside Houston, publicly accused Nassar of sexual abuse.

In a statement, Biles said it "breaks my heart even more to think that as I work towards my dream of competing in Tokyo 2020, I will have to continually return to the same training facility where I was abused."

Biles' Olympic teammate Aly Raisman as well as others who have accused Nassar of abuse have criticized USA Gymnastics, the U.S. Olympic Committee and Michigan State University saying those organizations did not do enough protect the young athletes from Nassar.

Nassar is awaiting sentencing after pleading guilty in November to multiple counts of sexual assault that occurred while he was employed by Michigan State and USA Gymnastics. He faces a minimum of 25 to 40 years in the molestation case under a plea deal. He's already been sentenced to 60 years in federal prison for child pornography crimes.

More than 120 girls and women have given statements so far at Nassar's five-day hearing.

The Associated Press contributed to this report.