Rioting broke out Saturday night at punk rock concert, injuring several people and destroying two police cars, officials said.

Some in the crowd of about 1,500 at the "British Invasion 2K6" show pelted police with rocks and bottles, forcing the officers to withdraw, police spokesman Sgt. Rick Lindsey said.

Two concertgoers were hospitalized with serious injuries, and two officers suffered minor injuries, he said.

The rioting began when police responded to a report of a stabbing at the National Orange Show Events Center concert. When officers arrived, the crowd became agitated and several fights broke out, forcing the officers to back off, Lindsey said.

After backup arrived, the officers went in again and extracted the stabbing victim and another person who was beaten, Lindsey said. But the violent crowd forced officers to withdraw again.

With additional backup, including Los Angeles County sheriff's deputies and Fontana police, officers lined up in phalanx formation to clear the streets and they fired pepper balls and tear gas to move the crowd, Lindsey said.

As the crowd dispersed they destroyed two police cars and vandalized area businesses, Lindsey said. A trash bin was set on fire and storefront windows were smashed.

The all-day concert was scheduled to feature 22 punk rock bands, including G.B.H. and the Adicts.