Four buildings at Harvard University's campus in Cambridge, Massachusetts, have been evacuated over reports of explosives on site.

The prestigious US university said it is investigating the unconfirmed reports and police have been called to the scene.

Harvard Tweeted:

The university stressed that no explosion has occurred.

"The Harvard University Police Department (HUPD) this morning received an unconfirmed report that explosives may have been placed in four buildings on campus: the Science Center, Thayer, Sever and Emerson Halls," a university spokesperson said.

"HUPD and Cambridge Police are on the scene. Out of an abundance of caution, the buildings have been evacuated while the report is investigated. Harvard's focus is on the safety of our students, faculty and staff."

WCVB television reported the alert was sparked by a suspicious package.

More to follow ...