ORLANDO, Fla. — Close to 600 students in a senior-level business course at University of Central Florida must retake a midterm exam after a professor was tipped off to cheating.

Students who admit to cheating will be given the chance to complete the course if they attend an ethics seminar, Professor Richard Quinn told students.

Those who don’t step forward will be found out anyway, Quinn promised during an emotional lecture.

The incident, Quinn told students, has left him “physically ill, absolutely disgusted” and “completely disillusioned” after 20 years of teaching.

All the students — even those who didn’t cheat — must take the rewritten midterm exam by midnight Wednesday. Students who are found not to have cheated will be able to keep the higher score of the two.

Cheaters typically risk disciplinary action that could include expulsion, university officials say.

But Quinn brokered a deal with the business dean that would allow students to clear their records if they owned up to cheating before the rewritten exam started being administered Monday morning.

An investigation is under way to determine how students got their hands on the exam key in advance. All faculty have been alerted about the apparent security breach, Quinn told students.

Someone anonymously dropped off a copy of the exam key at Quinn’s office not long after the exam was given earlier this month. Some students also were starting to complain about classmates who were bragging about acing the exam because they had copies of the exam key.

Quinn reviewed exam scores and discovered it is likely that one-third of the students in the strategic management course cheated. He decided not to cancel the course because it would be unfair to students who did not cheat.

But he did toss the exam scores for everybody. Faculty members have rewritten the midterm — 200 questions — so the exam key for the original test is useless. The final exam still to be given has also been rewritten, Quinn told students.

Quinn was not immediately available for comment.

“The days of being able to find a new way to cheat the system are over,” Quinn told students. “This type of behavior cannot, will not be tolerated.”

“It’s disappointing these actions took place,” UCF spokesman Grant Heston said of the apparent cheating, but the incident demonstrates policies in place to detect cheating are working.

UCF has testing labs that are monitored to deter cheating.