With the exception of a few careless students walking inside to empty classrooms, most people left North Hall on Thursday afternoon, as a 45-minute fire alarm caused the building’s three wings to be evacuated.

At about 1:30 p.m., a third-floor main electrical panel overheated, causing light smoke to emit from a fixture in the hallway, Capt. Wes Herman of the UCSB Station 17 firehouse said. Firefighters responded to the scene, but found no evidence of an actual fire.

Herman said UCSB Facilities Management activated the building’s main alarm after receiving a call from faculty on the third floor, which reported that smoke was coming out of the ceiling panels in the hall. Firefighters opened windows to let the smoke out of the building.

As of Thursday afternoon, a representative from Facilities Management could not be reached for comment on why the panel had overheated.

The vast majority of students and faculty promptly left the building when the alarm began. About 100 to 200 people paced outside, waiting to return to class or to their offices. However, a few individuals went back inside despite the loud alarm and presence of fire engines, an ambulance and several UC Police Dept. officers.

One student at the scene briefly stood in front of North Hall’s north-facing entrance, looked around and then entered the building despite the alarm.

Such actions, besides being careless, endanger others, Herman said. He said that while heading to the third floor he encountered a man still in the building.

“I scolded him pretty hard,” Herman said.

Refusing to evacuate a building puts firefighters at risk, as they will have to reenter a building to forcibly remove individuals, he said.

“Those kind of guys kill firefighters,” Herman said.