Authorities estimate at least 15,000 people attended the annual party on Saturday. Deltopia draws crowds in the thousands every year, mainly students from UC Santa Barbara and surrounding colleges.
Before the trouble even started, law enforcement had arrested 56 people and issued 49 citations. At least 44 people were taken to the hospital for injuries, including alcohol poisoning.
Things escalated about 8 p.m. when sheriff's deputies responded to two stabbings.
Shortly after that, the crowd got unruly. A UCSB police officer was hit in the head with a backpack full of liquor bottles. Two sheriff's deputies were also injured: one was cut by a bottle, and the other had a brick thrown at his head.
Several people in the crowd began tearing down traffic signs, throwing objects and even lighting mattresses on fire.
Law enforcement used tear gas, pepper spray and rubber bullets to try control the chaos. The rioting continued until nearly 1 a.m., when law enforcement was finally able to break up the crowd.
The Associated Press contributed to this report.