"A few" people suffered minor injuries in the blast at California Hall, a university spokesman told the Los Angeles Times. One victim was taken to a hospital, he said.
"The power outage and explosion were due to a power system failure. All are asked to leave the main campus area immediately," the university said in a statement.
"The campus is experiencing a power outage. All classes this evening are canceled. Lab operations should be safely shut down and people should leave the building. At this time, most major IT services ... are offline. When power returns, these systems will gradually come online."
Berkeley Fire Department Chief Gil Dong told school newspaper The Daily Californian it appeared an underground electrical vault exploded at about 6:40 p.m.
The Times said the explosion happened after a power outage was reported at 4:30 p.m.
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