The school said Monday it evacuated the buildings. There have been no explosions.
The four buildings cited by the university on its Twitter account were the Science Center, and Thayer, Sever and Emerson halls.
"Out of an abundance of caution, the buildings have been evacuated while the report is investigated," the university said at its website. "Harvard's focus is on the safety of our students, faculty and staff. We will update the media when we have more information."
Final exams are underway at the university.