Harvard University has reopened four buildings on campus after evacuating them this morning due to a bomb scare, the Harvard Crimson reports. Sever Hall, Thayer Hall, and Emerson Hall were all cleared in time for afternoon exams, and Harvard Yard was reopened before 2pm. An email tip prompted the threat, reports the Boston Globe, but a Harvard police spokesman refused to confirm. No explosives have yet been found. The school posted alerts on its emergency page and its Twitter account, clarifying that there were no reports of actual explosions, and that the evacuations were ordered out of an "abundance of caution."