The main 2 groups involved here are the Nortenos who are American born Latins and the Surenos who are Mexcian nationals.Similar fighting was reported from San Jose and is expected for San Francisco and Oakland

http://www.ktvu.com/news/4457729/detail.html

Vandalism, Fights Erupt During Richmond Cinco De Mayo Celebration

POSTED: 10:55 pm PDT May 5, 2005

RICHMOND -- Richmond police Thursday evening closed down a main thoroughfare and made several arrests after Cinco de Mayo celebrations erupted into fighting and vandalism, according to police Sgt. Mark Gagan.

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Video On Demand: Richmond Cinco De Mayo Celebration Erupts In Melee



From 4 p.m. until about 8 p.m., there were no problems reported as people drove down 23rd Street honking horns and waving flags. Gagan said there were between 1,200 and 1,500 in the crowd.

Around 8 p.m., he said about a dozen fights were observed breaking out in the crowd. Because of the fights, and because people in cars were reportedly ignoring requests to let passengers in and out, police shut down the street around 8:30 p.m.

At that point, Gagan said half the crowd left and about 500 people began congregating in the middle of 23rd. Some threw bottles at police, according to Gagan.

Unable to control the crowd, the city's Mobile Field Force was called in, and the crowd was slowly pushed down side streets and into the city of San Pablo, Gagan said.

Surveying the area where the crowd had been, police found that most of the windshields of cars at a dealership had been broken.

Police arrested one person for fighting, and detained several others who have since been released.

No serious injuries were reported, but reports of property damage are still being received. Police don't yet know the full extent of damages that occurred tonight, Gagan said.