Oprah Winfrey said Monday she wept for half an hour when she heard a dorm matron was accused of abusing students at her school for disadvantaged South African girls. She promised to "clean house" starting with the headmistress.

Calling the allegations of abuse at a school she founded in South Africa "one of the most devastating, if not the most devastating experience of my life," Winfrey appeared as part of a press conference detailing the investigation of child abuse which led to the arrest of a school employee.

Last month, a 27-year-old dormitory matron at the Oprah Winfrey Leadership Academy south of Johannesburg, South Africa, was suspended in connection with allegations involving indecent assault and soliciting under-age girls to commit indecent acts.

Tiny Virginia Makopo faces 13 charges of indecent assault, assault and criminal injury committed against at least six students aged 13-15 and a 23-year-old at the school.

"When I first heard about it I spent about a half-hour going around my house crying," Winfrey said at a news conference.

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Makopo said she was innocent when the charges were read during a bail hearing in Johannesburg. The magistrate released her on bail of $450, but she is restricted in her travel and contact with others. She left court today, with a court appearance ordered for December 13.

Winfrey founded the boarding school near Johannesburg last January - but by March, parents said students at the academy were being treated as virtual prisoners, permitted little or no means to communicate beyond its walls, CBS News correspondent Dean Reynolds reports.

Today, over the satellite hookup from Chicago to Johannesburg, Winfrey acknowleged that a system designed to protect students had become a way to intimidate them, Reynolds reports.

Winfrey said she was grateful to finally being able to speak about the events, as police investigators has asked her to remain silent while the investigation was being conducted so as not to jeopardize the case.

Winfrey said she was informed on October 6 by Samuel that fifteen girls had come to his office to see him with a list of grievances, including suspected sexual abuse of one of their classmates. The suspect was immediately removed from campus.

"I was, needless to say, devastated and really shaken to my core when I first heard this news," Winfrey said.

She spoke with the founder of the Child Trauma Center in Houston, Dr. Bruce Perry, who informed her that, under U.S. law, suspected child abuse must be reported to child protective services, which is also the case under South African law, so she alerted Superintendent Andre Needling and told him that there was suspicion of some kind of sexual abuse.

"I told Andre that I wanted to conduct an independent investigation to determine what exactly had happened and that I would appreciate his advice and his guidance in this matter." Needling said his department would work in cooperation with the school's investigation.

The reason for hiring an independent investigative team, Winfrey said, was "because my experience with child predators is that no one ever, ever abuses just one child.

"Although the girls only had spoken of one classmate, my first priority was to determine how many girls had actually been affected and to what extent."

A team of three investigators, lead by Robert Farley, commander of the Child Exploitation Unit of the Cook County Sheriff's Office, flew from the United States and spent a week interviewing students and staff. Winfrey precede the investigators, companied by Dr. Perry, and she spoke to all of the girls personally, encouraging any who had been harmed to come forward.

"I told them that although they had apparently been living in an atmosphere that repressed their voices, that this was a chance for them to break the silence and to take their voices back."

By the next day, five other girls had stepped forward.

Because the girls were afraid of repercussions from the remaining dorm matrons, Winfrey said, all remaining dorm matrons were removed; teachers were placed in rotation in the dorms.

On the weekend of October 14, with the information collected, calls were placed to the parents to inform them of the situation, and a meeting was arranged for the following weekend. Winfrey returned to South Africa and met with the parents and daughters, apologizing for the "unfortunate circumstances."

"I promised to institute immediate changes to create a new model of excellence in social, emotional and academic life for girls at the

school."

At the press conference in Johannesburg, John Samuel, chief executive of the academy, said that this has been a difficult time for the school community, but that "We are beginning to heal.

"The girls who have been affected have received and continue to receive the best counseling and support, and all of our learners are getting support from the academy, their peers, and their families. On campus, there is a sense of relief that the investigation has concluded and we are returning to a normal way of life.

"The spirit of the girls remains strong."

"This has been one of the most devastating, if not the most devastating experience of my life," Winfrey said, "but like all such experiences, there is always much to be gained, and I think there is a lot to be learned.

"I'm also very grateful to their parents and to their guardians and their caretakers for their continued trust and their support in me and also in the school.

"What I know is, is that no one - not the accused, nor any persons - can destroy the dream that I have held and the dream that each girl continues to hold for herself."

Superintendent Andre Neethling, from the police's sexual offenses and child protection unit, told the news conference that there had been at least three serious cases of indecent assault and that the abuse had taken place over four months.

The star talk show host said officials at the Oprah Winfrey Leadership Academy for Girls hid facts from her and told students to "put on happy faces" and not complain to her.

She said the school head mistress's contract would not be renewed and indicated others also would be dismissed.

Winfrey said she was not responsible for hiring at the school but that the screening process was inadequate and "the buck always stops with me."

Few issues resonate as deeply with Oprah Winfrey as child sexual abuse, notes Reynolds, so it's no wonder that this episode has come as a great shock to her and her millions of fans.

It was at the $40 million school in the Gauteng Province founded by Winfrey, a school with an enrollment of largely underprivileged young girls, where the abuse allegedly took place.

At the opening of the Oprah Winfrey Leadership Academy in January amid great fanfare, the television personality said, "I wanted to educate girls because I was a poor girl, a poor girl who grew up with my grandmother, as so many of these girls."

But by March complaints were starting to surface. Several parents charged that their children were being held as virtual prisoners at the school, with visits limited to one a month, and with cellphone and e-mail use tightly restricted.

The issue is a personal one for Winfrey, herself a victim of sexual abuse. On her show in 2005, she confided to viewers, "I was shameful for so many years and I realized the reason I was ashamed is because I took responsibility for [my abuse]. I blamed myself for it. So you can release the shame when you realize that it wasn't your fault."

In a statement released over the weekend, Winfrey told the students, whom she calls "her girls," that it isn't their fault, either.

"It is my deepest hope that the accused is brought to justice. ... Any time a child has the courage to step forward, it is our duty as adults to listen and take immediate action."

Parents of the schoolgirls want the punishment to fit the alleged crimes.

"I think she must take a long sentence," said Masechaba Hine, mother of two girls who attend the academy. "She is okay to rot in jail."