San Francisco (CNN) -- Police in riot gear moved into the Occupy Oakland encampment Monday, tearing down tents and arresting some protesters, the latest effort by city officials across the country to gain control over a movement that some leaders say has become a public safety and health threat.
Oakland, California, police, aided by dozens of officers from nearby jurisdictions, arrested 32 people in the effort to clear Frank Ogawa Plaza near City Hall before dawn, Interim Chief Howard Jordan said. There were no reports of injuries or complaints of abuse, he said.
The camp had become an unbearable drain on city resources, an economic threat to nearby businesses and a danger to public safety, Mayor Jean Quan said.
"The encampment became a place where we had repeated violence and this week a murder. We had to bring the camp to an end before more people were hurt," she said.
The developments in Oakland come amid rising concern from city officials around the country that the protests drain resources and threaten public health. What started as the Occupy Wall Street movement in New York in September has spread across cities worldwide as a call to action against unequal distribution of wealth and other issues.
In Oregon, Portland police made more than 50 arrests Sunday as they cleared two parks -- Chapman and Lownsdale Square -- of protesters.
Police called in reinforcements from surrounding jurisdictions, and more than 300 officers took part in the sweep -- which went off without incident, authorities said.
"We acted proactively," Portland Mayor Sam Adams told reporters on Monday. "We were not going to wait until somebody died in a camp."
He thanked police and other city employees for their work and encouraged protesters to find a new outlet.
"I hope that this Occupy Wall Street movement will focus and pivot and realize its potential as a national and international movement.," he said.
In Philadelphia, Mayor Michael Nutter said Sunday that what started as a peaceful protest 39 days ago has given way to increasing public safety and public health concerns.
"Occupy Philly has changed," Nutter said. "We're seeing serious health and safety issues playing out on an almost daily basis. ... The people of Occupy Philly have also changed and their intentions have changed. And all of this is not good for Philadelphia."
A woman reported she was sexually assaulted Saturday night in a tent at the encampment, Nutter said. CNN affiliate WPVI reported a suspect was arrested in the alleged assault.
The mayor also cited the threat of fire near historic City Hall and concerns about litter, public urination, defecation and graffiti.
Numerous reports of thefts and assaults in the encampment have been made, and 15 emergency medical runs were made between October 6 and November 11, he said.
Protesters are also blocking a planned $50 million renovation at Dilworth Plaza, where they are camping, threatening jobs of workers on the project, Nutter said.
The protesters are "purposely standing in the way of nearly 1,000 jobs for Philadelphians at a time of high unemployment," Nutter said. "They are blocking Philadelphians from taking care of their families."
"We have things we need to do," Nutter said. "I understand that they have things on their mind as Americans and wish to express their free speech. I understand that, I get that, I've defended that. The things we're talking about, the activities that are going on, are not about free speech. They're public health and public safety concerns that have nothing to do with Wall Street and corporations."
In Denver, police arrested three protesters on Sunday, a day after taking 17 people into custody in a dispute over clearing furniture and tents that city officials said were blocking a right of way.
Police in Tulsa, Oklahoma, arrested six people and issued four citations for remaining in a park past curfew Sunday night, Officer Jason Willingham said.
In Nashville, authorities dismissed charges against 55 Occupy protesters who had been given trespassing citations. The protesters had been demonstrating at the state Capitol grounds.
The prosecutor in the case asked that the charges be dismissed, and the judge agreed, Tennessee General Sessions Court administrator Warner Hassell said.
The Oakland operation has cost the city $2.4 million to respond to Occupy events, a statement from the Oakland's Emergency Operations Center said Monday.
City officials plan to clean up the plaza and reopen it to protests.
Jordan said city officials will enforce a ban on camping in the park with an around-the-clock police presence. But he said peaceful demonstrators would be allowed to remain at the site around the clock, if they wished, so long as they don't bring tents, sleeping bags or other "lodging equipment."
"If you're not breaking the laws, we're not concerned about your presence," he said.
The plaza was one of two Occupy camps in the city. The other, at Snow Park, remained standing. Jordan said police would not move against that camp on Monday, but added it could be dismantled later.
Protesters are meanwhile looking for a private space from which to protest, city officials said.
The decision to clear the plaza prompted a longtime friend of Quan who described himself as her legal adviser to resign.
"No longer Mayor Quan's legal advisor. Resigned at 2 am. Support Occupy Oakland, not the 1% and its government facilitators," attorney Dan Siegel said in the post, which Siegel confirmed to CNN was accurate.
City spokeswoman Susan Piper described Siegel as a "volunteer adviser."
CNN's Shawn Nottingham, Rick Martin and Melanie Whitley contributed to this report.