A powerful explosion rocked UC Berkeley on Monday evening, forcing authorities to evacuate the sprawling campus and leaving four people with minor burns, school officials said.
The blast and fire north of California Hall, which forced students to scramble for safety and sent a dark cloud of smoke into the air, was probably caused by the theft of copper wire from an off-campus electrical station, a UC Berkeley spokesman said.
One of the victims was taken to a hospital; the others declined to be transported. About 20 people were rescued after being trapped in elevators, officials said.
Students and a campus worker recalled hearing a loud boom and seeing flames as buildings went dark and people screamed from elevators that were stuck between floors.
"It was dark. It was pretty scary. We just wanted to get out of there," said Jesse Kay, 20, a sophomore who had left the weight room.
Jay Reddy, 19, was in an electrical engineering class in the basement of Cory Hall when "all the power went out." He said emergency lights were working and some daylight was coming through a window as the instructor finished. "We had to figure out how to get out of the building," Reddy said.
The blast was reported about 6:30 p.m., roughly two hours after a power system failure, UC Berkeley spokesman Dan Mogulof said.
He said the stolen copper wire was discovered last week and repaired Sunday.
"We have a strong suspicion that what happened is related to vandalism discovered last week," Mogulof told reporters. "The damage they caused may have been far more extensive than we originally thought."
He said the blast area was two stories high and two roadway lanes wide and sent at least one manhole cover shooting into the air. Ripping the wire out of the system required a lot of force and probably special equipment, Mogulof said. The explosion took place as engineers were attempting to bring power back up.
"Something happened here that surprised the experts," he said. "Somebody attacked our system. Somebody stole key parts of our system."
The campus remained dark Monday night except for the lights of police vehicles patrolling the area and emergency generators providing power for research projects.
Mogulof said classes "aren't going to happen and people aren't going to come back here until we're sure we have a safe situation."
Times staff writer Robert J. Lopez contributed to this report.