Update 10:50 a.m.: Police say they have arrested four activists for chaining themselves together to block the entrance to the county administration building in downtown Oakland.
Police are threatening more arrests at the Alameda County Administration Building as more than 100 protesters demand an end to what they say is a collaboration between county law enforcement and the U.S. Immigration and Customs Enforcement.
The protesters are beating a drum chanting "the people united will never be defeated" in English and Spanish.
The group is also demanding an end to the Urban Shield SWAT training exercises, and to stop a planned expansion of a jail east of San Francisco.
Original Post: (AP) - A May Day rally in San Francisco is underway with people blocking vehicle access at the Immigration and Customs Enforcement Office in downtown. They say they plan to stay there until police arrest them.
Streets around the Sansome Street office are closed as a few hundred residents, immigrants, youth, and workers march in the area. Some buses have been rerouted and motorists are advised to avoid the area.
May Day marches are planned in cities spanning from Santa Rosa to San Diego.
Immigrant advocates say they hope large crowds will get Trump and congressional lawmakers to rethink efforts to expand deportations and pressure local governments to assist federal deportation agents.
Around the world, union members traditionally march on May 1 for workers' rights. In the U.S., the event became a rallying point for immigrants in 2006 when more than 1 million people marched against a proposed immigration enforcement bill.