Tens of thousands of people are expected to gather Saturday in Los Angeles and throughout Southern California in a day of protest.

Police have declared an unlawful assembly near the Metropolitan Detention Center in downtown Los Angeles, urging people to avoid the area, according to a public safety alert issued Saturday evening.

Organizers said "at least 8 million people gathered today at more than 3,300 events across all 50 states," from big cities and small towns.