The number of demonstrators snowballed as Occupy Seattle marched from downtown to major access points to the Port of Seattle in Sodo, where more than 500 people are now bracing to shut down access, Jen Graves reports from the scene. Here's the crowd next to the West Seattle Bridge:

Three people have been arrested so far, Jen says. Hundreds more are currently staged around several gates spread out over about a mile as a shift-change approaches in about an hour; if they engage in a major act of civil disobedience, she says, it will be during the shift change. Meanwhile, the place is swarming with cops: on foot, on bikes, on horseback, and in at least two paddy wagons. \

"Cargo has been rerouted to somewhere else, an occupy organizer says, so OS is declaring it a success," Jen says. "Terminal 18 has been shut down, they're saying."

The city is warning of a traffic tangle. "Occupy Seattle protests combined with a Monday evening football game have the potential for creating major traffic issues this afternoon on roads and highways in the area south of downtown," says a notice just sent by SDOT. "Commuters should expect travel delays and allow additional time for detouring to other routes. "