The Harvard College administrative board is reviewing the allegations of "academic dishonesty," ranging from "inappropriate collaboration to outright plagiarism, on a take-home final exam," dean of undergraduate education Jay Harris said in a note sent to students.
A comprehensive review of every exam from the class found that nearly half of the 279 enrolled students may have worked together in groups to develop and share answers.
Harris said the magnitude of the case is "unprecedented in anyone's living memory."
The students whose work is under review have been contacted by the board, which will meet with each student separately seeking to understand all the relevant facts and to determine whether any faculty rules were violated.
Students found responsible of academic dishonesty could face disciplinary actions including withdrawal from the college for a year.
"We take academic integrity very seriously because it goes to the heart of our educational mission," said Michael Smith, dean of the Faculty of Arts and Sciences, who sent a letter to the FAS faculty to outline actions the faculty can take to reinforce Harvard's academic policies.
"Academic dishonesty cannot and will not be tolerated at Harvard."
While neither the course nor the name of students allegedly involved was revealed, Harvard Crimson, the university's student newspaper, said the students were enrolled in the 'Introduction to Congress' class taught by assistant professor Matthew Platt.
"These allegations, if proven, represent totally unacceptable behaviour that betrays the trust upon which intellectual inquiry at Harvard depends," said Harvard University president Drew Faust.
"We must deal with this fairly and through a deliberative process. At the same time, the scope of the allegations suggests that there is work to be done to ensure that every student at Harvard understands and embraces the values that are fundamental to its community of scholars."
The allegations surfaced last semester when the faculty member teaching the course questioned the similarities between a number of exams and referred them to the board.
After reviewing the exams and interviewing students who submitted them, representatives of the board initiated the broader review in consultation with the faculty member.
The board has not come to any judgment about specific cases.
Smith cautioned that the allegations should not lead people to draw broad conclusions.
"We must also not forget that the vast majority of our students complete all their assignments honestly, diligently and in accordance with our regulations and practices," Smith said.
"Allegations of inappropriate collaboration or plagiarism in a single class should not be allowed to diminish the good work or reputation of our outstanding student body."
The administrative board is responsible for evaluating requests for exceptions to academic policies and review of students' academic performance.