UC Berkeley explosion: When will Berkeley be back to normal?

Power has been restored to most of the University of California, Berkeley, but some classes remained canceled a day after an underground electrical vault exploded, injuring several people and prompting a campus evacuation, school officials said on Tuesday.

Chancellor Nicholas Dirks posted a message on the university's website assuring students and staff, "It is safe to come to campus," though he listed 11 buildings still without electricity as of late morning, including Doe Memorial Library and California Hall in the center of campus.

"Students should assume that classes in these buildings are canceled for the day, but classes in other campus buildings will take place as planned," Dirks said.

The explosion and power outage occurred late Monday afternoon on the north side of California Hall, school officials said. Engineers began restoring electricity about two hours later.

One person was taken to a hospital with minor injuries, while two or three others hurt by the blast declined medical assistance, according to a statement on the school's website.

The Contra Costa Times reported on Tuesday that four people suffered minor burns, with three treated and released without going to the hospital, and about 20 people trapped in elevators, some for up to nearly four hours.

"Power to the majority of the campus buildings was restored last night using a methodical approach to ensure that each building is safe to occupy," Dirks said. "Because of this method of restoration, the campus has a high level of confidence that the campus is safe."

Campus spokesman Dan Mogulof said Monday that the explosion appeared to stem from damage to the university's electrical system caused by vandals stealing copper wiring.

(Reporting by Laila Kearney; Writing by Steve Gorman; Editing by Cynthia Johnston and Leslie Adler)