Administrators would not reveal the name of the class or even the department, saying that they wanted to protect the identities of the accused students. The Harvard Crimson, the university’s student newspaper, reported that it was a government class, Introduction to Congress, which had 279 students, and that it was taught by Matthew B. Platt, an assistant professor.

Professor Platt did not respond to messages seeking comment.

When final exams were graded in May, similarities were noticed in the answers given by some students, officials said, and a professor brought the matter to the administration immediately. Over the summer, Harvard’s administrative board conducted an initial review, going over the exams of all of the students in the class for evidence of cheating. It concluded that almost half of them showed signs of possible collaboration.

“The enabling role of technology is a big part of this picture,” Mr. Harris said. “It’s the ease of sharing. With that has come, I believe, a certain cavalier attitude.”

The university said it planned to increase efforts to teach students about academic integrity.

“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,” Harvard’s president, Drew Gilpin Faust, told The Harvard Gazette, the university’s official newspaper.

Harvard’s student handbook says that students must “comply with the policy on collaboration established for each course,” and notes that such policies vary from department to department, from class to class, and even from assignment to assignment within a class.