OAKLAND (CBS / AP) — Occupy Wall Street protesters had just half a day to celebrate what they saw as their biggest victory so far: a daylong gathering in Oakland that drew thousands of people and led to the peaceful shutdown of the nation’s fifth-busiest port. Then, after midnight, the vandalism began.

Hours after a small group of what city leaders called “provocateurs” clashed with riot police, set fires and shattered windows early Thursday, demonstrators across the country condemned the violence and wondered whether it was a turn that would destroy their cause.

READ MORE: Improving Weather Conditions Allow Crews to Increase Containment of Fawn Fire to 35 %

“They don’t speak for the majority of people who were here yesterday,” said Hadas Alterman, a college student who was gathering trash at a tent camp near Oakland City Hall. “That was an hour of action, and we were out here for 12 hours and it was peaceful.”

The 3,000-person protest outside the port Wednesday night represented an escalation in tactics as demonstrators targeted a major symbol of the nation’s commerce with peaceful rallies and sit-ins, managing to effectively suspend maritime operations there for the night.

Related Coverage:
Photo Gallery: Occupy Oakland General Strike
Occupy Oakland Protest Coverage

The street spasm that followed when about 200 people tried to take over a vacant building, however, raised questions about whether a movement with no organizational structure and no high-profile leaders can—or should—do anything to stop those they called troublemakers.

On Thursday afternoon, representatives from the Occupy Oakland media committee read a statement saying participants supported the goal of reclaiming empty buildings to serve the public but regretted that their daylong downtown demonstration was marred by an “autonomous” group.

“It is unfortunate that the unprecedented mobilization and engagement of tens of thousands of our neighborhood in this beautiful Oakland city should be marred by broken windows and graffiti,” Laura Long said, reading the statement. “Occupy Oakland does not advocate violence and has no interest in supporting actions that endanger the community and possibilities that it has worked to build.”

The group released a statement Thursday night saying it doesn’t support vandalism but would not take an official position until Friday’s night “General Assembly” meeting.

So far, few cities have reached the level of Oakland, a unique place with a long history of tensions between residents and police.

Bob Norkus at the Occupy Boston camp said the riots didn’t represent the broader movement and likely wouldn’t have a lasting effect on it, either. The movement is still evolving and mistakes are inevitable, he said.

It “has to be nonviolent, or else it will just end. We won’t get the support,” he said. “It doesn’t mean you can’t agitate people. But you can’t also be breaking windows and burning.”

Police in riot gear arrested dozens of protesters in downtown Oakland, where bands of masked protesters took over a vacant building, erected roadblocks and threw chunks of concrete and firebombs. Five people and several officers were injured.

Oakland officials said 103 people had been arrested by 3 p.m. Thursday, including two 17-year-olds who were cited and released.

Chris Hedges, who was demonstrating at Goldman Sachs’ headquarters in New York, said the clashes in Oakland are a reminder to protesters that they should only respond peacefully to police actions.

“It’s awful. But police want people to break windows and set cars on fire, because it’s the kind of thing they know how to master—with force,” he said before being led quietly away in handcuffs.

Raymon Curtis, who was protesting in Portland, Ore., said he doesn’t believe the police in his city are seeking violence.

“I looked in their eyes and at first I thought it was a hard look,” Curtis said. “Then, I realized it was the same look I had when I went to prison for the first time. They’re terrified.”

Some protesters said violence can bring attention to the cause.

“This thing has to escalate so people see the violence and who is protecting the interests of the corporations,” said Denver protester Dwayne Hudson, standing next to a grill with logs burning over charcoal to stay warm after a snowstorm.

The far-flung movement challenging the world’s economic systems and distribution of wealth has gained momentum in recent weeks, with Oakland becoming a rallying point after an Iraq War veteran was injured in clashes with police last week.

READ MORE: Teen Driver Injured in Solo Crash Near San Gregorio

Organizers called for a general strike on Wednesday, and supporters in New York, Philadelphia, Los Angeles and elsewhere held smaller-scale demonstrations, some in solidarity with their Oakland counterparts.

Protesters in Oakland and in other cities viewed the day’s events and the port shutdown as a significant victory.

Police, who had little to no presence during the protest during the day, said about 7,000 people participated in largely peaceful demonstrations. There were a few incidents of vandalism at local banks and businesses.

An accounting of the financial toll from the port shutdown was not immediately available.

A protest organizer in Chicago, Joshua Kaunert, said the shutdown was an “amazing” event for the movement, but he didn’t want to speculate on what effect the violence would have. He said the lack of a formal leadership structure—and the emphasis on what he called a “true, direct democracy”—makes it difficult to weed out potential troublemakers.

“As a movement, it is definitely hard to keep that kind of element away, but that’s a double-edged sword,” Kaunert said. “If you want true, direct democracy, you’re going to have issues, regardless.”

The movement’s tent camps in public parks have drawn all types of people, including the homeless, families and anarchists.

At the Oakland encampment, Hale Nicholson, who described himself and others as pacifists, said he participated in Wednesday’s demonstration and march to the port and then went to sleep at the camp around 9:30 p.m. Around 1 a.m., he said, he was awakened by the sound of flash-bang grenades.

A group of protesters broke into the former Travelers Aid building in order to, as some shouting protesters put it, “reclaim the building for the people.” They voiced anger over budget cuts that forced the closure of a homeless aid program.

They blocked off a street with wood, metal Dumpsters and other large trash bins, sparking bonfires that leapt as high as 15 feet in the air. Several businesses were heavily vandalized. Dozens of protesters wielding shields were surrounded and arrested.

Police said they used tear gas and beanbags to disperse the crowd.

Brenda Jamison, a mother of four who lives downtown, watched the disturbance from her window and prayed for it to stop. She said the police acted appropriately when they tried to separate the disruptive protesters causing damage from the peaceful masses.

“I don’t feel like I’m home,” she said. “It’s not an issue of black and white. You just have these people who come out looking for an excuse to tear up everything. It’s not right.”

Protesters and police then faced off in an uneasy standoff until the wee hours of the morning.

It is the kind of posture that Oakland is familiar with, with clashes erupting during the 1960s-era protests over the Vietnam War and the draft, among other issues. More recently, in 2009 and 2010, the city was the scene of violent demonstrations over the killing of an unarmed black man by a white transit officer. Downtown businesses were looted, windows smashed and fires set.

Then, as now, police blamed the violence on a small group of anarchists, many from outside the city.

Officials said 18 windows were broken in the area of the violence. About two dozen businesses had damaged storefronts. Most of them were chain stores, including Burger King and Foot Locker.

People who participated in the daytime protests returned to help sweep up debris and scrub off graffiti.

Shari Rivers, the manager of a Tully’s Coffee located on the city hall plaza, was busy cleaning up Thursday morning after protesters broke windows, stole some property and knocked over the cash register overnight.

“I cried. It’s very disheartening. I am part of the 99 percent and have supported this movement,” she said, adding that she blamed the city for letting the protest get out of hand. She added, “This shouldn’t happen in a U.S. city.”

MORE NEWS: Homeless Man Found Dead with Gunshot Wounds Near Creek Trail

(Copyright 2011 by CBS San Francisco. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)