A power outage struck campus Thursday evening, causing evacuations in the J. Paul Leonard Library and residential buildings for a couple hours.

Lights first shut down at approximately 8:43 p.m. and emergency backup lights came on several seconds later until power was restored.

PG&E representatives said they were still analyzing the reason for Thursday’s power outage and that it could be weeks before a reason is found, said University spokesperson Ellen Griffin Monday.

“At this point we have no definitive explanation of the cause. We know that there were two PG&E lines that come into the campus and that one of them tripped, but we don’t know the cause,” Griffin said.

A Library Community Service Officer made an announcement at 8:46 p.m ordering people in the J. Paul Leonard Library to evacuate until further notice. Other buildings on campus were also evacuated, including the residential dorms.

At first inspection, the outage only affected SF State and not the surrounding community. The cause of the power outage was unknown, according to Library Community Service Officer A. Juarez. Police cruisers roamed around campus with flashing lights as a large number of people made their way off of campus.

Psychology student Vicky Palacios said she was surprised when lights in the quiet study area first went off and waited to see how others around her reacted before she left the library.

“I was just going to stay in there, there was some lights that came back on,” she said.

At 9:02 p.m., another announcement was made by LCSO Juarez in front of the east entrance to the library.

“We don’t know exactly what happened and we need to keep the library clear,” Juarez said. “We don’t know exactly how long this will take. I’ll keep you guys updated, and it is all for security purposes.”

As the full moon kept the night lit outside of the library, some evacuees waited patiently for new information.

“I’m going to give it 30 minutes because I don’t have anywhere else to do work,” said Palacios, who commutes from the Excelsior District and was planning to stay in the library until the last bus came.

The lights went back on around 9:24 p.m. in the Mary Park and Mary Ward Residence Halls, according to resident assistant Kaylie Gutierrez. She and another resident assistant were performing duty rounds, checking elevators for trapped students and making sure everyone was safe.

Gutierrez said the Area Assistant Coordinator was currently dealing with the lockout situations of several students who ran out of their dorms to see what the commotion was about.

“Everyone gets so excited when a blackout happens, when anything different happens,” Gutierrez said.