Police fired stun grenades and rubber bullets as hundreds of disappointed University of Arizona fans overturned vehicles Monday and set at least three afire.
Several people were apparently hit, including a Phoenix television reporter, though the extent of their injuries was not clear. Riot officers seemed to meet with little resistance, although they continued to move down the street in formation, banging their shields with their batons.
"Now this is a riot," Assistant Police Chief Roberto Villasenor said as officers moved in to break up a crowd at a major intersection near the campus.
An estimated 2,000 fans had spilled into the streets after Arizona lost the NCAA championship to Duke in Minneapolis.
Police said initially there was little problem and only a handful of minor arrests.
But then about a 1,000 people jammed an intersection near the campus, and a motor home and least two other vehicles were burned, some after having been overturned. With the damage escalating, police - in riot gear - ordered the crowd to disperse and then moved in shoulder to shoulder.
Students mostly gave way as the police approached. One individual sat still in the middle of the street and was taken into custody.
Later police fired stun grenades to help disperse the crowd and fired rubber bullets, striking some individuals. At least one could be seen holding his head.
One person reportedly was treated at a hospital for facial wounds from allegedly having been thrown into a window, and one officer suffered an ear injury, Villasenor said.
Villasenor said six people were arrested on varied charges that included assault, trespass, criminal damage and disorderly conduct.
Police had cordoned off the entire campus by closing streets to vehicular traffic, a precaution to avoid having motorists trapped as some were during the 1997 postgame action.
Villasenor said there had been several small fires along the main avenue, where he estimated about 2,000 people milled about at one point, and that there were four other small fires at Jefferson Commons, a student housing area about four miles away.
There also were reports of shots but no injuries at a bar on the edge of the campus, and some students set off fireworks, police and others said.
It was unclear how many cars were damaged. Police had reported one overturned near the campus early on, and Pima County sheriff's deputies had reported another was overturned about 10 miles away.
Roughly two hours after the Wildcats fell to Duke, rowdy fans on Fourth Avenue - a popular downtown Tucson venue - tipped several vehicles, set an recreational vehicle on fire and overturned streetlights.
An explosion at 10:12 p.m. Tucson time outside the Hut, 305 N. Herbert Ave., sent spectators running and activated nearly 500 extra police officers in full riot gear to disburse the crowd.
Police detained several people.
No major injures have been reported.
Earlier, Tucson police officers and firemen were dispatched to an area just west of the Student Recreation Center where another vehicle caught fire.
More information will be updated here as the Wildcat reports through the night.