After a massive day-long street party fueled by alcohol, the "Deltopia" event in Isla Vista turned violent late Saturday night, with law enforcement struggling to quell what they described as a "major incident" and "unlawful assembly."

At least six officers were injured, struck by rocks and bottles, according to Santa Barbara County Sheriff's Department spokeswoman Kelly Hoover.

Witnesses were using the word "riot" to describe the conditions on the streets of the community adjacent to UCSB.

[UCSB Student Offers Perspective on Deltopia Mayhem: Click Here]

Tear gas and rubber bullets were being deployed as deputies and officers working to regain control of the streets.

Shortly after 11 p.m., Hoover said deputies and other law-enforcement personnel were dealing with a major incident in the vicinity of Sabado Tarde and Camino del Sur, as well as problems in other parts of the community.

Approximately 18 people were arrested during the disturbance, Hoover said.

"The whole incident started in the 6700 block of Del Playa Drive," Hoover said, adding that a UCSB police officer was injured at that location shortly before 10 p.m., and a large crowd — "an unlawful assembly" — formed shortly thereafter.

"The UCSB police officer was hit in the head with a backpack that contained large bottles of alcohol," Hoover said. "During the arrest, a large crowd gathered for several blocks and threw objects at law enforcement personnel, including rocks, bricks and bottles."

At least five other officers also were injured, Hoover said,

"One was hit in the face with a brick, and two others were hit in the hand with bottles," she said. "Approximately 26 people were transported to area hospitals."

Emergency radio traffic indicated there was at least one officer down in the vicinity of Del Playa Drive and Camino Corto, but details were not immediately available.

Unofficial reports indicated the officer suffered only minor injuries.

At one point, all fire personnel and paramedic units were directed to leave Isla Vista due to the disturbances, according to emergency radio traffic.

Paramedics were being escorted by police to attend to people who were injured or suffering from alcohol poisoning, according to emergency radio traffic.

Law enforcement was calling in back-up from the California Highway Patrol, the Lompoc and Santa Maria police departments, and other jurisdictions, Hoover said.

Personnel from Ventura and San Luis Obispo counties were placed on stand-by, she said.

Multiple stabbings were reported earlier in the evening, but details on those incidents were not available.

A mattress was reported on fire in the middle of the road in the area of Trigo Road, but firefighters were holding back because a large crowd had formed and it was not safe for them to enter the area.

A message from the UCSB emergency notification system, sent at 11:14 p.m. warned people to stay out of Isla Vista:

"There is an incident of civil unrest in Isla Vista. It is recommended that no one attempt to enter Isla Vista if you are not a resident. At this time Del Playa is closed to everyone."

Emergency radio traffic included a constant stream of medical calls, most for alcohol poisoning.

Saturday's late-night disturbances provided a violent end to a day the began quietly enough but included plenty of problems.

Isla Vista began filling up just after noon Saturday, as thousands of young people ignored the sidewalks, most traveling down the road with nothing but the clothes on their backs.

In a sea of colorful bikinis, board shorts and flip flops, hordes of young people descended on the small campus community for the annual "Deltopia" block party dressed like it was any other beach day — likely expecting they wouldn’t be able to feel the cool ocean air when the festivities carried into evening.

Most didn’t figure out until they arrived that all the beaches were actually closed in anticipation of the weekend event, a spin-off of the former “Floatopia” gathering on the sand that led to scores of arrests and medical calls, and left the beach covered with trash and human waste.

After Santa Barbara County officials took the preemptive step of closing down the beaches, the party moved up to Del Playa Drive in 2010, and Saturday’s crowd was shaping up to at least match last year’s 15,000 revelers.

Law enforcement uniforms were easy to spot, since more than 100 extra officers were on hand to monitor the number of people inside residences and on balconies.

Throughout the course of the day and evening, more than 100 people were arrested, and at least 44 people were transported to the hospital. Hoover said.

There had been 17 calls for medical service, and out of those 14 were transported to the hospital.

All the transports were alcohol-related and several involved subjects who had alcohol poisoning, Hoover said.

Shortly before 8 p.m., there was a report of two people who had been stabbed on the 800 block of Camino del Sur, but that could not immediately be confirmed.

About 12,000 partiers kept authorities busy Friday night as well, prompting approximately 36 arrests and 88 citations, including 26 for drunk in public, 47 for minor in possession of alcohol, and 22 open containers, according to Kelly Hoover, a spokeswoman for the Santa Barbara County Sheriff’s Department.

Authorities were also called out to a report of someone in distress in the water around 3 a.m. in the 6700 block of Del Playa, but no one was found, Hoover said.

More than half of Friday’s citations were issued to students who said they were from out of the area.

“The weather is perfect for the event,” Hoover said Saturday. “We’re seeing a large crowd, and we may see more than we had last year.”

Students from across the state walked the streets in search of a house party, unfazed by the towering, portable camera poles authorities installed in time for the event.

“This is pretty crazy,” said Christopher Paul, who was visiting from Monterey. “Girls are flashing people. This doesn’t happen in my life.”

A visiting officer from UC Riverside said he expected most people to be drunk by 4:30 p.m.

“You guys need a joint? Right?” a passerby joked to the officer, who was working from 5 a.m. to midnight.

Many students used their cell phones to find their friends — some belligerently drunk by early afternoon — and one reveler said he was selling water for $20 a pop.

“I don’t want to be wet!” a girl shouted after a boy wearing a cowboy hat squirted her with a water gun.

Authorities stopped and cited a San Jose State University student for carrying a purple plastic cup with alcohol in it, a common violaton throughout the celebration.

Last year, authorities issued 23 arrests, 71 citations and had 44 people transported to the hospital, with 440 total calls for service.

Officers this year paid special attention to folks near the beaches and to those dancing on apartment balconies, since last year’s event was marred by the death of a woman who fell from the cliffs, and a balcony collapse that sent several people to the hospital.

The sheriff’s Search & Rescue Team planned to be in Isla Vista all weekend, along with paramedics, County Fire and county emergency medical services to coordinate the walk-in first aid shelter at Embarcadero del Mar and Trigo Road.

Check back with Noozhawk for updates to this story.

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