STATE COLLEGE, Pa. (AP) _ A weekend arts festival turned ugly when Penn State students and alumni rioted after bars closed, tearing down street lights, smashing storefronts, even stripping naked and burning their underwear.

About 1,500 people took part in the melee early Sunday, which ended after police used tear gas and nightsticks to break up the crowd. Twenty-four people were arrested and 14 officers were injured. Three storefronts and 33 street lights were damaged. Property damage was estimated at $50,000.

``This is probably ... the most property damage of any incident I can remember in my 25 years at Penn State,'' said Tom Harmon, director of Penn State police services.

``It was very ugly in terms of the crowd's behavior toward police. The officers early on, when we were just lined up across the road and before we moved on the crowd, took a lot of flying objects,'' he said.

The disturbance is the latest uprising involving college students. There were at least 10 major police clashes with partying students this year, including one on May 1 in East Lansing, Mich., where thousands of Michigan State students rioted after the school banned drinking at a popular spot.

The Penn State incident occurred as tens of thousands of people descended upon the college for the annual Central Pennsylvania Festival of the Arts, a popular summer reunion of students and recent graduates.

The riot began around 1:30 a.m. as bars announced last call on a street lined by high-rise apartments popular among students. It ended more than two hours later.

The cause for the riot is unclear. According to police, about 150 people converged after a Frisbee game and became upset when told to disperse. Someone in the crowd threw a trash can into the street and set it afire, and within 10 minutes the crowd ballooned to 1,500 people.

``It didn't seem all that violent, sort of like a pep rally but with fire,'' said Penn State freshman Marc Clair.

``I saw a couch on fire, a girl burned her bra. ... It was pretty crazy,'' Penn State junior Greg Pezza said.

But witnesses said the conflict began when police confiscated, then returned, a ``party ball'' _ a miniature keg of beer.

Streets reopened by 8 a.m. Sunday for the last day of the festival.