The gas leak was reported at about 7:30 a.m. at the main campus in the area of McClintock Avenue, between Childs and Downey ways. Gate 6 was closed to vehicles and pedestrians.
Chris Gilbride, a spokesperson for Southern California Gas Company, said an excavation damaged a two-inch plastic natural gas service line, which resulted in the leak.
Gilbride said the leak was under control shortly before 9 a.m. USC officials urged the public to stay away from the area during repairs.
Fire officials said evacuations ended by 9:30 a.m. No injuries were reported.