The violence broke out in the densely populated beachside community of Isla Vista around 9:30 p.m. Saturday during the annual spring break party known as Deltopia, held near the University of California, Santa Barbara and attended by 15,000 people, the Santa Barbara County Sheriff's Office said.
Sheriff's spokeswoman Kelly Hoover said things escalated after a campus police officer was hit in the face with a backpack filled with large bottles of alcohol.
Authorities said some members of the crowd began throwing rocks, bricks and bottles at officers, lighting fires and damaging law enforcement vehicles.
"It was an emergency situation where we had to call in mutual aid," Hoover said. "They have had civil disturbances before in Isla Vista, but it has been many years since something like this."
Authorities reported using tear gas, pepper spray and foam projectiles to disperse the surging crowd.
One university officer and five deputies were injured, including one who was hit in the face with a brick and two others who were both hit in the hand with bottles, sheriff's deputies said. One will require surgery for his hand, Hoover said.
It was not immediately known Sunday how many people remain in custody or were still being treated at the hospital.
"Deltopia attracts out-of-towners who come in and are not invested in our community and there are some who come to cause trouble," Hoover said.
The situation had stabilized by Sunday morning after deputies received backup support from multiple agencies in neighboring Ventura County.
Isla Vista borders the university and is known for partying. The half-mile area has roughly 23,000 residents, of which 60 percent are students.
Hoover said authorities remained in the area Sunday morning cleaning up broken glass and trash strewn throughout the neighborhood.