The 53-page lawsuit alleges that the school failed to protect the victims of Dr. George Tyndall, who is accused of improperly photographing female students during exams and inappropriately touching them.
"Today, we have amended our lawsuit to reflect that we are suing on behalf of 24 women who alleged that they were victims of Dr. Tyndall," Allred said at a press conference while two of those female students sat beside her.
The two victims also gave statements detailing Tyndall's behavior.
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The U.S. Department of Education is investigating whether USC concealed sexual harassment allegations made against the doctor.
Tyndall retired last year and has denied any wrongdoing.