Story highlights A 2007 report found Tutwiler had the highest rate of sexual assault among prisons for women

The group says women reported "frequent and severe officer-on-inmate sexual violence"

No comment from Alabama Department of Corrections or attorney general's office

Equal Justice Initiative wants Justice Department to investigate Tutwiler Prison

Male guards at an Alabama women's prison engaged in the widespread sexual abuse of female inmates for years, a nonprofit group alleged in a formal complaint filed with the Justice Department on Tuesday.

The Equal Justice Initiative asked the Justice Department to investigate alleged incidents occurring between 2009 and 2011 at the Tutwiler Prison for Women in Wetumpka, Alabama. The federal agency confirmed that it received the complaint though declined further comment.

"In interviews with more than 50 women incarcerated at Tutwiler, EJI uncovered evidence of frequent and severe officer-on-inmate sexual violence," the Montgomery-based group said in a statement.

"This troubling cycle of abuse and lack of accountability has established a widespread pattern and practice of custodial sexual misconduct," said Bryan Stevenson, the group's executive director.

Stevenson also blamed the Alabama Department of Corrections for under-reporting the alleged attacks, which the group says include rapes, and for responding inadequately.

The group claims that more than "20 Tutwiler employees have been transferred or terminated in the past five years for having illegal sexual contact with prisoners."

"It's an ongoing thing, a daily thing," said Stefanie Hibbett, 31, a former Tutwiler inmate. "You see women raped and beaten, and nothing is ever done."

Hibbett said she was the victim of sexual assault in November 2010. She said she told the prison's warden about the assault, but no charges were ever filed against the prison guard she says attacked her. An Alabama judge dismissed a civil suit she filed in the case in August.

Several imprisoned women also allegedly became pregnant after being raped by guards, giving birth while in custody, the nonprofit group reported.

CNN cannot independently confirm that account. The Alabama attorney general's office referred questions to the Alabama Department of Corrections, which did not immediately return a call for comment.

A 2007 Justice Department report found that Tutwiler maintained the highest rate of sexual assault among prisons for women and 11th overall of those evaluated across the United States.