Jamie Dantzscher, a member of the 2000 Sydney Olympic US bronze medal squad, was joined in coming forward publically by Jessica Howard, the US national rhythmic gymnastics champion from 1999 through 2001, and Jeanette Antolin, a US team member from 1995 to 2000.
Dantzscher was first seen by Nassar at age 13 after she earned a spot on the US junior national team but complained of back pain.
"He would put his fingers inside of me and move my leg around," Dantzscher told CBS. "He would tell me I was going to feel a pop and that that would put my hips back and help my back pain.
Antolin said she only realized last year what she thought was treatment had been abuse.
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"It was like a light bulb went off," Antolin said. "I trusted this man. Just knowing how vulnerable I was as a kid, to not know something like that would be inappropriate, just ruined me."
John Manly -- a California attorney representing more than 40 women in a lawsuit against USA Gymnastics for failing to protect his clients -- says Nassar may have abused hundreds of girls over more than two decades, many at the ranch training headquarters of famed US coaches Bela and Marta Karolyi.
"This is somebody who is a serial predator. But the story here is that no one was watching to protect these girls, and they (USA Gymnastics and the Karolyis) put medals and money first."
Nassar, 53, was arrested last November on charges of sexually assaulting a child in Michigan, where he is being held without bail. In December he was indicted on federal child pornography possession charges.
Nassar, who treated elite US gymnasts as Olympic team physician from 1996 to 2015, is accused by former athletes of inserting ungloved fingers into their anuses and vaginas and fondling their breasts.
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The women who came forward detailed a high-pressure, emotionally abusive atmosphere at Karolyi Ranch where girls feared that to complain might doom their Olympic dreams.
"The pressure that they put on you, to be perfection for them, it was very overwhelming and stressful," Antolin said, adding it was understood that speaking out "hurts your chances."
"No one wants to step out of line because there's a group of people that make decisions that dictate whether you're successful or not. So you just comply with and do what you're told to do."
"You can't say anything," Howard said. "If you do, there's a chance you are going to get in trouble and the last thing you want to do is bring more trouble onto yourself on purpose."
Dantzscher said Nassar brought snacks and candy and built trust, a confident when the stress of Olympic training wore them down.
"I always felt like I got in trouble," she told CBS. "I wasn't working hard enough. I was told to lose weight. At one point, I started making myself throw up.
"He was like my buddy. He was on my side. I felt like we weren't allowed to even smile in the gym, so getting treatment, him just joking around and talking about how horrible they (coaches) were, it was kind of like a bright light."
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"It was an environment of fear," Manly said. "And he stepped in and became the good guy. He gave them candy. He gave 'em encouragement. He acted like he cared about them. No one else there gave that impression."
Dantzscher said she was left alone with Nassar and felt certain the Karolyis knew it.
"They had to know," she said. "There was no one else sent with him. And that's the thing, too... The treatment was in the bed -- in my bed that I slept on."
The Karolyis, in a statement to 60 Minutes from attorney James Christian, denied "the existence of a 'toxic' environment."
It also said the Karolyis were "never aware" Nassar would perform the procedures described or that he visited athletes in rooms without supervision.