Cambridge, Mass. (AP) -- Harvard University has reopened all four buildings that were evacuated after police received an unconfirmed report that explosives may have been placed inside.
Students have been told they may return to the Science Center, the last of four buildings to be cleared. The final clearance was issued Monday afternoon through Harvard's emergency alert system.
The FBI was investigating, along with Cambridge and university police and other agencies.
Harvard officials would not say how they received the report and would not comment on speculation among students that it could have been a hoax timed to coincide with finals week at the Ivy League school.
Students were first informed of the report shortly after 9 a.m., just as some finals were about to get underway.
Harvard University says four buildings on its campus outside Boston are being evacuated because of unconfirmed reports of explosives. The school tweeted that there have been no reports of any explosions.
Three of the buildings being evacuated in Cambridge border Harvard Yard.
The school posted alerts on its emergency page and its Twitter account. They say that both school and city police are investigating, and the university will provide more information soon.
Harvard says in a statement that its university police department received the unconfirmed report that explosives may have been placed in the four buildings and they were evacuated out of an abundance of caution.
Final exams have begun at the Ivy League school.