The explosion happened in an underground vault outside California Hall. The blast sent flames shooting up into the air. The explosion occurred inside one the campus's 14 electrical vaults, near the chancellor's office.
"I heard a loud boom and I heard some young woman scream," said student Nicholas Karas.
"We saw at least one person thrown to the ground by the blast. People were very concerned. Some people ran forward, some people urged everyone to back off. We, in general, the crowd eventually backed off and retreated to north campus," said student Tiffany Ng.
U.C. Berkeley spokesperson Dan Mogulof said it all started after PG&E crews discovered someone had stolen electrical grounding copper wire late last week from an off campus manhole that feeds into the university's system.
Investigators now say that by stealing the copper wire, the person/people responsible did more damage than they had initially thought.
"Our system here is underground and that led to the power outage yesterday at around 4:30 p.m.," said Mogulof.
The explosion occurred as crews were trying to power back up.
Some students say the university's alert system didn't work the way it should have.
"Didn't actually get any text messages for about half an hour," said Ng.
"This is a community of 50,000 people so we need to see, at some point, did that distribution of information fail to reach all the people it could have," said Mogulof.
"There's a definite chance of my classes being cancelled tomorrow and we have a midterm Monday, so it might be pushed back as well, so we really don't know. It's up in the air," said student Hayley Laity.
Late Tuesday afternoon power generators were being put in to bring power to those affected buildings.