At about 9:30 p.m. bottles were thrown, resulting in at least one arrest involving assault with a deadly weapon. Another suspected gang member was found with a concealed knife, Austin said.

About two dozen deputies and Santa Rosa police officers worked at the festival.

The festival, in its ninth year, celebrates Mexican heritage, music and food. Organizers estimated 7,500 to 10,000 people attended.

It's held each year at the old Albertsons parking lot on Sebastopol Road.