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Rick Bowmer, Associated Press
Occupy Portland protester Carsen Harrison-Bower sleeps while being chained to a 50-gallon drum filled with rocks and concrete after spending another night in Terry Schrunk Plaza, Monday, Nov. 7, 2011, in downtown Portland, Ore. Protesters are handcuffed to a piece of metal inside the barrel in Terry Schrunk Plaza, which is on federal property.

PORTLAND, Ore. — Mayor Sam Adams has warned the sprawling Occupy Portland encampment to address its issues with drugs, violence and other criminal conduct.

"The way things are operating now is not sustainable," Adams wrote in an open letter to demonstrators. "I know there is a nationwide Occupy process for working through those things, which I want to give some time to work. But we cannot wait long."

The letter, sent late Monday, linked problems in the Occupy Wall Street protests in other camps to criminal activity, including a death in Vancouver, British Columbia, that has been attributed to a drug overdose.

The 300-person encampment in downtown Portland began after an Oct. 6 march. Since then, the camp has struggled with issues of violence and theft that accompanied a flood of homeless and mentally ill people drawn to free food and shelter.

On Monday, Portland police released a series of charges filed against protesters ranging from menacing to reckless burning to disorderly conduct. Protesters say the problems in camp aren't unique to Occupy Portland — they're the problems of the homeless and mentally ill that manifest themselves in the encampment.

The police said Tuesday that year-over-year crime increased 18 percent in the neighborhoods bordering the encampment. Between Oct. 6, 2010, and Nov. 6, 2010, police responded to 488 offenses.

In the same monthlong stretch in 2011, police responded to 578 cases. The increases were found in disorderly conduct, larceny and simple assault cases. The increase in crime is set against the fact that 300 people are living in an area that typically empties out after 6 p.m. during the week.

Tensions rose a week ago, during a protest in which police allege a protester shoved an officer into a moving bus. The officer was injured but not hospitalized.

Organizers said they're trying to determine the feasibility of removing the worst offenders from camp in an effort to restore order and focus to the movement. Decisions are made by consensus at all-camp meetings held every evening, and an emergency meeting held Sunday attempted to address security concerns.

No decisions have been made, but protesters are considering taking pictures of the offenders and posting them in the security and kitchen tents. People who repeatedly violate camp law would be removed and would not be eligible for the camp's free meals.

Christopher Dunn, 22, said he never expected the camp would attract drug users and others with criminal intentions.

Dunn said the camp's current security procedure is to go tent to tent, checking on protesters. Members of the camp's security team have radios and can call in problems to each other while patrolling.

Adams said the encampment needs to determine where it goes next.

"I know that Portland is not unique in facing these real issues around camps. But I hope we are unique in our solutions," Adams wrote. "I believe Occupy Portland can lead the nation in figuring out what the next phase of the Occupy Movement looks like."

Some organizers said removing people is at odds with the movement's goal.

"I'm kind of saddened by it a little bit," said organizer Micaiah Dutt. "This issue of drug abuse and homelessness, we can't even begin to have social change if we're not willing to work with the people that are here."

Dutt said he would vote against any proposal to exclude people from camp.

"A revolution doesn't come on a silver platter," Dutt said. "It's called struggle for a reason. I refuse to be the first generation of radical activists that walks away from struggle because it's too hard."

Nigel Duara can be reached at http://www.twitter.com/nigelduara