It was a discarded cigarette that likely caused a small fire on the UNO campus Tuesday evening. For students and faculty -- all the smoke made it look worse than it was.

More than 300 people evacuated the Arts and Sciences Hall as firefighters tore a wood frame from the outside of the building near the North door.

"A security officer came in and said, ' Ladies, this isn't a drill!'" says Autumn Spurck who was on a computer at the time. "We looked down the hall and we could see smoke and I could smell it."

The students wondered if classes would resume or if they could even go back to retrieve their stuff.

"For tonight, Arts and Sciences Hall is closed to activities..." announced Tim Kaldahl, UNO University Relations.

It's not certain but firefighters couldn't help but notice the number of cigarettes dropped right next to where the fire started.

"Hopefully, it's a lesson for everyone to more careful when discarding their cigarettes when finished," says Omaha Battalion Chief Chris Greger.

Security video didn't pick up just how smokey it was in the halls, but it did show a couple students trying to put out the fire with a fire extinguisher.

Meanwhile, with no injuries and minor damage there may be a teaching moment for the university.

"We try to discourage smoking in and around buildings as much as possible but it's something we haven't figured out how to eliminate," says John Amend, UNO Director of Facilities.

The Arts and Sciences building is expected to reopen Wednesday morning.