(Adds details about evacuation)
BOSTON, Dec 16 (Reuters) - Harvard University on Monday warned of "unconfirmed reports" of explosives planted at four buildings on its Cambridge, Massachusetts campus.
The school said it evacuated the Science Center, Thayer Sever and Emerson Halls.
"Out of an abundance of caution, the buildings have been evacuated while the report is investigated," the Ivy League school said on its Web site.
Harvard's campus is located in a crowded urban area adjoining Boston. (Reporting by Scott Malone; Editing by Richard Valdmanis and Chizu Nomiyama)