The University of Oklahoma says it has determined that fraternity members learned a racist chant at a national "leadership" event organized by Sigma Alpha Epsilon four years ago — and that it was then "formalized" at the local chapter.

"It is clear that during the four years since the chant was brought to University campus, its existence was known by recent members and that it became part of the institutionalized culture of the chapter," the school wrote in a report on the episode.

At a press conference Friday, OU President David Boren released the results of the college's investigation into the chant, which was caught on a viral video. He announced that 25 students will be disciplined, in addition to the two who were expelled.

"We also today want to a send a message to the rest of the country ... this is a problem in America. We’ve had an epidemic of racism all across our country," Boren said.

"We can stop it — if all of us and the institutions and organizations we belong to say we have zero tolerance for racism in America. That's not who we are in America as a people."

College investigators interviewed more than 100 SAE members to track the origin of the chant, which was sung to the tune of the children's ditty, "If You're Happy and You Know It" and which vowed that no African-American would be a member of the frat.

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"The chant was learned by local chapter members while attending a national leadership cruise sponsored by by the national SAE organizations four years ago," Boren wrote in a letter to the SAE national organization.

"While there is no indication that the chant was part of the formal teaching of the national organization, it does appear that the chant was widely known and informally shared amongst members on the leadership cruise."

The report says that "over time, the chant was formalized in the local SAE chapter and was taught to pledges as part of the formal and informal pledgeship process."

High school students — potential recruits invited to a "Founders Day" event — were on the bus when the song was sung. Those teens had also been at the frat house, where alcohol was "readily available," the report said.

Boren shut down the OU chapter after a viral video of the chant came to light. He said other students who were on the bus or officers of the frat must perform community service or undergo cultural sensitivity training.

The officers of the chapter also met with black student leaders in Boren's office, "baring their souls" and apologizing, for 90 minutes before the press conference, the college president said.

In his letter to SAE's top officials, Boren asked the organization to disclose whether they have looked into how widely the chant was taught or used in chapters across the country and what steps it has taken "to remedy the situation."

The national fraternity said in a statement Friday it has "no current evidence that the chant is widespread across the fraternity’s 237 groups."

"We remain committed to identifying and rooting out racist behavior from SAE, and we are actively investigating all of our local organizations to determine whether there are issues in any other location," Executive Director Blaine Ayers said in a statement.

Ayers said the organization is conducting its own investigation, and will release the results. "The song is horrific and does not at all reflect our values as an organization," Ayers said. "If we find any other examples of this kind of behavior currently occurring, we will hold our members accountable, just as we’ve done in Oklahoma."

The expelled OU students, Levi Pettit and Parker Rice, have apologized for leading the chant. Parker has said the song was "taught to us," though Pettit refused to say where he had learned it.

"I'm here to apologize for what I did. The truth is that what was said in that chant is disgusting," Pettit said at a press conference earlier this week where he was flanked by black leaders.

The OU chapter of SAE has hired an attorney — the same lawyer who represented Oklahoma City bomber Timothy McVeigh — for a possible lawsuit to get it reopened and ensure the students' rights are protected.