An investigation is under way at the University of Central Florida to determine how students obtained the exam key in advance, The Orlando Sentinel reported Monday.
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 come forward will be found out anyway, Quinn told the class during an emotional lecture.
The cheating incident, Quinn told the students, left him "physically ill, absolutely disgusted" and "completely disillusioned" after 20 years of teaching.
The entire class -- even those who didn't cheat -- must take the rewritten midterm exam by midnight Wednesday, Quinn announced.
Students who are found not to have cheated will be able to keep the higher score of the two.
Students who cheat normally risk disciplinary action that could include expulsion, university officials say.
But Quinn negotiated a deal with the business dean that would allow students to clear their records if they owned up to cheating before the rewritten exam was administered.
A review of exam scores showed it likely that one-third of the students in the strategic management course cheated, Quinn said.