HUNTSVILLE, Texas -- Disgraced ex-sports doctorand a former trainer were charged with sexual assault Friday following an investigation involving an elite gymnastics center in Texas. A grand jury indicted Nassar on six counts of second-degree sexual assault of a child, Walker County prosecutor Stephanie Stroud announced during a news conference. She said a former trainer, Debbie Van Horn, was charged with one count.
The charges stem from an investigation at the famed gymnastics training center run by Bela and Martha Karolyi north of Houston. Five former gymnasts implored authorities last month to determine whether the Karolyis could have prevented abuse at their since-closed gymnastics ranch. Two gymnasts said Nassar abused them there.
"There are no criminal charges against the Karolyis at this time. We don't believe at this time there's any corroborated evidence to support criminal charges," Stroud said, adding that the Karolyis have been cooperative during the investigation.
But, she added, "It's our belief that there was a total failure by (USA Gymnastics) to protect athletes."
In May, former gymnasts Jamie Dantzscher and Jeanette Antolin told "" they were sexually abused by Nassar for years, often while training at the Karolyi Ranch in Texas.
"We're not backing down, we're not going away," Dantzscher told CBS News' Omar Villafranca. "We're going to keep fighting until the right people are held accountable for the mistakes they've made."
"They had to have known. They knew everything else about everything else we were doing," Dantzscher said.
"If they didn't know that we were being abused, they still knew that a grown man was coming into a child's room at night time by himself," Jeanette Antolin said.
Two-time Team USA Olympic gymnast" last year that there should be major changes within USA Gymnastics. Raisman has accused Nassar of abuse.
"Why are we looking at why didn't the girls speak up?" Raisman said. "Why not look at what about the culture? What did USA Gymnastics do, and Larry Nassar do, to manipulate these girls so much that they are so afraid to speak up?"
Nassar is serving decades in prison for sexual assault and possession of child pornography in Michigan, where hundreds of women and girls accused him of sexually abusing them under the guise of medical treatment, including while he worked for USA Gymnastics, which trains Olympians, and Michigan State University.
Texas' governor ordered an investigation into what he called "gut-wrenching" allegations after the gymnasts came forward in Texas. The Texas Rangers are leading the Texas investigation, which also includes Walker County prosecutors and sheriff's officials.
The Karolyis have denied knowledge of any mistreatment.