OAKLAND (CBS / AP) — A crowd of at least 1,000 people, many holding candles, attended a vigil Thursday for the Iraq War veteran who suffered a fractured skull during a clash between demonstrators and police, while organizers prepared to defy Oakland’s prohibition on overnight camping at the site of ongoing Occupy Wall Street protests.

Shake Anderson, an organizer with Occupy Oakland, said half a dozen tents were erected on the plaza Thursday evening where police armed with tear gas and bean bag rounds disbanded a 15-day-old encampment Tuesday. More tents, food and supplies arrived during the meeting and vigil for Scott Olsen, with about 25 tents erected late Thursday.

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“We believe in what we’re doing,” Anderson said. “No one is afraid. If anything, we’re going to show there’s strength in numbers.”

Few police were seen in the area during the vigil or later during the night, though Oakland Mayor Jean Quan issued a statement asking protesters not to camp overnight at the plaza.

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In her statement, Quan also said that an investigation has begun into the use of force by police, including tear gas on Tuesday. She said she as “deeply saddened about the outcome on Tuesday.”

Olsen was transferred Thursday from the emergency room to the intensive care unit at Oakland’s Highland Hospital as his condition was upgraded to fair, said Curt Olsen, a hospital spokesman.

Dr. Alden Harken, chief surgeon at Alameda County Medical Center, said Olsen has improved dramatically since he was hospitalized unconscious Tuesday night with a bruised brain that was causing seizures.

By Thursday afternoon, Harken said the 24-year-old was interacting with his parents, doing math equations and otherwise showing signs of “high-level cognitive functioning.” The doctor said he may require surgery, but that’s unlikely.

“He’s got a relatively small area of injury and he’s got his youth going for him. So both of those are very favorable,” the doctor said.

Police early Tuesday cleared the plaza outside City Hall after it grew to dozens of tents and raised health and safety concerns among city officials. Later that day, officers and sheriff’s deputies from several Bay Area agencies clashed a second time in the streets with demonstrators angered by the move.

Oakland Police Chief Howard Jordan has promised an investigation into whether officers used excessive force during the second confrontation. He has also addressed Olsen’s condition, saying one focus of the review would be determining how the veteran was hurt.

Scott Olsen, Iraq War veteran, on ground bleeding from head wound after being struck by a projectile during Occupy Oakland protest. (AP Photo)

Olsen was marching with other protesters Tuesday night when he was injured, said Dottie Guy, of the Iraq Veterans Against the War.  Guy’s group said he was struck by some sort of projectile fired by police officers and sheriff’s deputies from multiple agencies who were trying to disperse the crowd that had gathered to protest the city’s decision to dismantle the demonstrators’ camp.

Dramatic footage of a bleeding Olsen being carried from the chaotic scene, marchers wading through clouds of tear gas and officers stained with paint thrown by some people in the crowd have sparked sympathy marches in other cities and criticism of the police.

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In a conciliatory gesture, the city on Wednesday allowed protesters back into the plaza but said people had to stay out of a fenced-off area that still was being cleaned and would have to leave the area by 10 p.m.

Hundreds of Occupy Wall Street protesters returned to the plaza and within hours, the fence had been torn down and stacked into an impromptu sculpture. But police maintained a minimal presence and only a small handful of people defied the curfew and stayed overnight.

“We have decided to have a minimal police presence at the plaza for the short term and build a community effort to improve communications and dialogue with the demonstrators,” Mayor Jean Quan said.

The Tuesday confrontations came as officials complained about what they described as deteriorating safety, sanitation and health issues at the camp.

The same concerns have been raised about camps in San Francisco and Los Angeles.

Protesters at San Francisco’s Justin Herman Plaza were bracing for a police raid early Thursday when they were visited by several city supervisors and a state senator. The officials expressed their support.

San Francisco police warned the protesters earlier in the week that they could be arrested on a variety of sanitation or illegal camping violations.

There were reports that police in riot gear had set up a staging area near the plaza early Thursday morning. But police spokesman Carlos Manfredi said officers routinely gather to practice crowd control procedures, and there were no plans to shut down the Occupy protest.

He said police were still seeking voluntary compliance.

“We’re still continuing to monitor the situation,” he said.

Anti-Wall Street protesters camped out in downtown Los Angeles say they’re planning to continue their demonstration indefinitely, although both they and the mayor’s office were eyeing alternate sites.

Occupy LA organizer Gia Trimble said the protest has swelled to nearly 500 tents on the lawn around City Hall and organizers are eyeing possibly moving the encampment to a larger piece of city property nearby in downtown Los Angeles.

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