After a day of investigation, authorities revealed discarded cigarette butts as the cause of the fire that sparked a mass evacuation of the University of Wisconsin’s Grainger Hall.

Madison Fire Department spokesperson Lori Wirth said the fire was caused when multiple cigarette butts that were not properly extinguished were thrown very close to the outside of the building.

“Maybe [the area outside] was being used as a smoking area,” Wirth said. “There were certainly multiple cigarette butts.”

She said the butts made their way into an opening in the building’s exterior, causing a fire within the wall. She said the fact the fire was within the wall made firefighters think the fire was electrical, which is why they used foam to extinguish it and were so cautious in letting people back into the building.

Wirth said the fire caused $10,000 worth of damage to the building. Although there was not a lot of visible destruction, she said a lot of patching has to be done when there is damage to an exterior wall.

People who smoke are encouraged to take extra caution with their cigarette butts, Wirth said. She added it is important to dispose of them in a place that is non-combustible, such as a specified cigarette container.

Wirth also stressed the importance of making sure cigarettes are fully put out before they are disposed of. Ideally, she said, they would be dunked in water.

Wirth said another concern was the difficulty of getting people out of the building. She said people were very uncooperative when being asked to leave.

UW sophomore Sam DeLuca said Monday he was waiting in line to get food when the alarms went off, but many students did not pay attention.

“Everybody thought it was a joke,” DeLuca said. “It said attention, attention, but everyone just thought it was a joke, like high school when somebody just pulled it.”

Wirth said this was one of the major problems with the evacuation. She said especially in large buildings, people will ignore alarms and wait for others to tell them to get out.

“Well, that’s what the alarm is telling you,” Wirth said.