Riot police fired rubber bullets as they tried to disperse a rampaging crowd in central Salt Lake City, venue of the Winter Olympics, early today.
More than 30 arrests were made, police said. The crowd of young people broke several shop windows, trashed a police car and broke windows at the courthouse.
"There have been no serious injuries to my knowledge. There was no gunfire. We used some less lethal munitions to disperse the crowd," Salt Lake City police spokesman Mr Scott Folson said.
The crowd went on the rampage around midnight when police tried to stop them drinking near a temporary bar set up for the Olympics, which end today.
Witnesses said the crowd started throwing rocks and bottles at the police. An area was quickly cordoned off by police cars and helicopters hovered overhead using searchlights as running skirmishes broke out in the city center.
"The trouble started because nobody else was going to be allowed into the Budweiser tent because it was closing at midnight," a youth calling himself G.A. said.
"Everybody was packed into the street and everybody started stealing each other's beer and throwing bottles. The police came and one of them was hit in the face by a bottle.
"The police started firing rubber bullets. Then the crowd got really wild and starting chanting "U S A" and hurling bottles at windows."
Normally there are strict regulations governing the sale of alcohol in Salt Lake City, the capital of Utah. The state largely follows the Mormon religion which frowns on alcohol.
The hotel housing the International Olympic Committee was cordoned off by troops carrying automatic weapons.
The center of the city has been flooded during the 17 days of the Games by crowds enjoying Olympic events, concerts and a party atmosphere.