Updated 9.07pm

HARVARD UNIVERSITY has reopened four buildings following a major evacuation of the campus after reports that explosives had been planted on the grounds.

Students and staff were evacuated after an email was sent to campus police at the Massachusetts university at 8.40am today [1.40pm GMT] claiming that explosive devices may have been hidden at four sites.

Student publication The Harvard Crimson report that an alert was sent to students shortly after 9am EST [2pm GMT]. Exams were due to take place in some of the buildings affected.

Federal and state police were called to the scene to investigate as some parts of the large campus were sealed off.

The executive vice president of Harvard this evening said an investigation is taking place to determine who was responsible for the threat.

In a message sent to Harvard staff and students, Katie Lapp said the buildings were closed due to an “abundance of caution”.

Police officers outside a building at Harvard University earlier today. (AP Photo/Josh Reynolds)

“I am relieved to report that no suspicious devices were found,” she said.

She thanked the Harvard University Police Department and the “many local, state and federal agencies who responded” to the incident.

“Safeguarding our community in this instance unfortunately required the disruption of exams and the evacuation of one of our freshman dormitories,” she said. “The HUPD, in close cooperation with state, local and federal agencies, is continuing to investigate this incident to determine who may be responsible”.

A security officers keeps people from entering Harvard Yard (AP Photo/Elise Amendola)

She reassured people that there is no viable threat to the university. “At this time, we know of no specific threat to campus and activities are returning to normal,” she said.

On its Emergency page at Harvard.edu, the university said that  it received “an unconfirmed report that explosives may have been placed in four buildings on campus: the Science Center, Thayer, Sever and Emerson Halls”.

Originally published 2.43pm

Additional reporting by Christine Bohan