(CNN) -

Harvard University said it has reopened several buildings after receiving a bomb threat.

Several buildings were evacuated at 9:30 a.m. on Saturday after a caller claimed he was armed and had placed bombs around the school.

About three hours later, the campus was given the all-clear notice. Authorities said they did not find evidence to substantiate the threat.

Officials say the buildings were evacuated "out of an abundance of caution." School officials say that Harvard and Cambridge, Massachusetts, authorities will continue to investigate the source of the phone call.