BERKELEY (CBS / AP) -- Power was restored to most of the University of California, Berkeley, on Tuesday as officials confirmed that the theft of copper cables from a substation caused a campus-wide outage that preceded an explosion and evacuation.
The blast occurred Monday night in an underground utility vault outside a building that houses the chancellor's office. It came as crews were trying to get the electrical system back up following an outage that darkened the campus for several hours.
Investigators have since traced the loss of power to a secluded access point away from the main campus that was damaged last week when someone tried to remove copper grounding cables, UC Berkeley spokesman Dan Mogulof said.
"In the course of trying to yank copper wire out of our grid, they caused damage, and yesterday's power outage was a direct result of that damage done," Mogulof said. "The explosion, however, it's not clear if that was a direct or indirect consequence of the damage."
A female student was treated at a hospital for minor burns, and three other people who were burned refused medical treatment.
Officials were relieved that the blast, which produced flames and a cloud of smoke at least two stories high and as wide as a two-lane street, did not injure more people, Mogulof said.
Eleven buildings, including the main library, athletic facilities adjoining the campus soccer and track stadium, and the arena used by the basketball and gymnastics teams remained without power.
More than 100 classes normally held in three of the affected buildings were canceled.
Public buildings and construction sites across the nation have been hit by copper thieves as the price of the metal has soared in recent years, Mogulof said it was apparently the first time UC Berkeley had been a target.
Officials became aware of the copper theft last week and thought the damage had been repaired on Sunday, Mogulof said. He refused to pinpoint the location, other than to say it was not visible from a road or walkway.
"It appears this was a sophisticated individual or individuals who knew what they are doing," he said. "It's not easy to pull out this type of copper wire, and they had something capable of pulling on cable so hard it flattened the cable."
During Monday's power outage, fire crews had to free about 20 people stuck in dormitory elevators. Students were able to sleep in the dorms, which have back-up generators.
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