The fire was reported at about 4:05 p.m. at the building known as the Old Administration Building, university spokeswoman Ellen Griffin said.
Firefighters responded and extinguished the fire within about 20 minutes, Griffin said.
People in both the Old Administration Building and the newer Administration Building adjacent to it had to be evacuated because of the fire and had not yet been allowed to go back inside as of 4:40 p.m., according to Griffin.
No one was injured in the blaze, which appears to be caused by the accidental igniting of materials on the roof, which was under repair, Griffin said.
An estimate on the damage to the building was not immediately available.