Reports are coming in, including from the Mercury's own Alex Zielinski, that there's been at least one arrest outside the small "expansion" of Occupy Portland tents in federally owned Terry Schrunk Plaza. And there's talk the Portland Police Bureau is activating its riot squad to deal with an emerging protest. (Nope; see below.)

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Check in on Twitter and Blogtown for developments. Sarah Mirk is headed down to the park, and we'll also be following on the Mercury's feed.

Update 4:16 PM: One update already from Sarah: The arrest so far wasn't actually related to Occupy Portland. Instead, Alex says, it involved a firearm-related charge. Some reports now say the feds have given protesters until 10PM to clear.

Update 4:18 PM The mayor's office saying that reports by KPTV and others that riot squad officers have been mustered are not true. It's regular officers on patrol, like they are on most events, alongside the Occupy Portland anti-coal-power zombie march.