Seattle police, downtown businesses prepare for possible May Day protests, violence (VIDEO)

SEATTLE -- Hundreds of police officers are expected to be on the streets of Seattle Sunday for May Day protests, and downtown businesses are being told to take tables and signs off the sidewalks and add extra security.

On past May Days, young protesters wearing masks have clashed with police and broken store windows and keyed cars parked on city streets.

The violence typically comes hours after the peaceful, organized marches held earlier in the day by labor unions and immigration reform activists.