An explosion that ripped through a building at UC Berkeley may be tied to the theft of copper wire that led to a power-system failure, a university spokesman said Monday night.
The 6:30 p.m. blast and fire at California Hall left four people with minor injuries. One person was taken to a hospital, UC Berkeley spokesman Dan Mogulof said.
About 20 people were believed trapped in elevators Monday night and waiting to be rescued, officials said.
The explosion sent smoke into the air and caused students to flee the campus, where evacuation orders were issued shortly after the blast.
Mogulof said officials suspect that a power system failure that preceded the blast was caused by the theft of copper wire from an electrical station off campus. The stolen wire was discovered last week and repaired Sunday, he said.
"The damage was far more extensive than we thought," Mogulof told reporters at the campus.
The power system failure was reported about 4:30 p.m.
The sprawling campus and dorm areas were dark, except for the lights of police vehicles patrolling campus and enforcing the evacuation orders.
It was unclear Monday night whether classes would resume Tuesday morning.
Video footage and photos on Twitter showed dark clouds of smoke visible from Sproul Plaza and what appeared to be a small fire burning in the background.
Someone on a loudspeaker could be heard saying: "This is the Police Department. Please exit campus," according to a video posted on YouTube.
[UPDATED 8:56 p.m.: All people trapped in elevators were rescued, the university said.]