An initial investigation by the Harvard College Administration Board of more than 250 final exams resulted in cases of alleged cheating involving "nearly half the students in the class."
Neither the course, nor the students were identified in the scandal, which would be one of the biggest at the Ivy League college.
According to the account, the allegations arose when a faculty member noticed "similarities between a number of exams." Anyone found to have cheated could face punishments including a one-year suspension from the college.
Michael Smith, dean of the Faculty of Arts and Sciences, said it was important to act.
"We take academic integrity very seriously because it goes to the heart of our educational mission," he said in a statement. "Academic dishonesty cannot and will not be tolerated at Harvard."
"These allegations, if proven, represent totally unacceptable behavior that betrays the trust upon which intellectual inquiry at Harvard depends," Harvard University President Drew Faust said.
"We must deal with this fairly and through a deliberative process."
Harvard, a college in Cambridge, Massachusetts, near Boston, is one of the most exclusive universities in the world, with students paying about $63,000 (50,000 euros) per year to attend.
Harvard said the cheating allegations were limited to one class, but that the incident had already prompted reforms.
The College Committee on Academic Integrity is to present "recommendations to reinforce the faculty's expectations of academic honesty," the Harvard news website said.
These could include "new ethics policies," possibly an "honor code" and consultations with outside experts, as well as discussions within student residencies.
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