Updated

Seven students have been punished for violating the code of conduct at Oprah Winfrey's school for disadvantaged girls in South Africa, the second controversy to hit the fledgling institution since it opened in 2007.

Winfrey representative Don Halcombe said Wednesday that four students were expelled and three were suspended last week from her Leadership Academy for Girls outside Johannesburg.

Halcombe declined to say what led to the violations because there are minors involved. Lisa Halliday, a spokeswoman for the academy's foundation, said it was a confidential school matter and would not "confirm any personal information or disclose any details related to these expulsions."

South African media have reported that the seven girls were accused of trying to force students into relationships and to engage in sexual contact.

"I'm disappointed that several of our students chose to disregard the school's rules," Winfrey said in a statement issued by her production company HARPO. "It's disheartening when any student has to be suspended or expelled and it's a process that involves serious review and consideration. We will not tolerate a violation of school policy and dishonesty."

This isn't the first time events at the elite girls school have upset Winfrey. The talk-show queen said she was devastated after a woman overseeing a dormitory at the academy was accused of abuse and sexual assault months after the school opened. The woman's trial has not yet ended.

The institution opened in January 2007 with about 150 girls in 7th and 8th grades. The Academy is expected to grow by one grade each year until it reaches full capacity in 2011, with approximately 450 girls in grades 7 through 12.

Winfrey poured $40 million into the 28-building campus, which is spread across 22 lush acres. It has computer and science labs, and a library, theater and wellness center. Each girl lives in a two-bedroom suite.

It's the fulfillment of a promise she made to former South African President Nelson Mandela and aims to give poor girls a quality education and prepare them for leadership positions in a country where schools are struggling to overcome the legacy of white-minority rule.