OAKLAND - Police clad in riot gear and armed with tear gas cleared out Oakland's anti-Wall Street encampment early Monday, the latest law-enforcement crackdown amid complaints around the country of health and safety hazards at protest camps.

The raid at the Occupy Oakland camp, one of the largest and most active sites in the movement, came a day after police in Portland, Ore., arrested more than 50 people while shutting down its camp amid complaints of drug use and sanitation issues.

Police in Burlington, Vt., also evicted protesters after a man fatally shot himself last week inside a tent.

Police staged a previous raid on the Oakland encampment Oct. 25, but Mayor Jean Quan allowed protesters to re-establish their tent city. On Monday, however, Quan said officials could no longer ignore the problems the camp posed.

"We came to this point because Occupy Oakland, I think, began to take a different path than the original movement," Quan said. "The encampment became a place where we had repeated violence and last week a murder. We had to bring the camp to an end before more people got hurt."

Demands increased for Oakland protesters to pack up after a man was shot and killed Thursday near the encampment at the City Hall plaza.

Protesters claimed there was no connection between the shooting and the camp. But police identified the slain man as Kayode Ola Foster, 25, of Oakland, saying his family confirmed he had been staying at the plaza.

Witnesses also told police that one of two suspects in the shooting had also been a frequent resident at the plaza. The names of the suspects have not been released.

Monday's raid came as no surprise to protesters after the city issued its fourth order to abandon the camp. About 300 officers from the Oakland Police Department and seven other law-enforcement agencies moved in around 5:30 a.m., arresting 33 people and tearing down about 150 tents.

Another man was arrested later in the morning for trying to break through police barricades and spitting on officers.

Protesters vowed to regroup and return.

"I don't see how they're going to disperse us," said Ohad Meyer, 30, of Oakland. "There are thousands of people who are going to come back."

Officials declared the operation a success, saying all arrests were peaceful and there were no reported injuries to protesters or officers. Police said those taken into custody likely will face charges.

Not everyone in Quan's camp agreed with the show of force.

Dan Siegel, one of the mayor's top legal advisers, resigned over Monday's raid, saying officials should have done more to work with protesters before sending in police. Siegel, a longtime friend of Quan who worked as an unpaid adviser, has been a vocal critic of Oakland police and their handling of the Oct. 25 raid. Video footage of a protest after that raid showed officers using flash-bang grenades and firing beanbag rounds, injuring a number of people.