ALAMO -- A high school graduation party turned violent Saturday evening, with up to 30 people brawling in the street, a Contra Costa Sheriff's spokesman said.

At least three people were injured, and one may have suffered a broken jaw.

Deputies got the call to the area near Red Wing Drive and Viking Place about 5:50 p.m., according to Sgt. Keith Chelini. When they arrived minutes later, the fight had already broken up and multiple vehicles had left the area, Chelini said.

The deputies were flagged down by a resident, who told them that they were the hosts of the party, and that several injured people were inside their house. Deputies interviewed witnesses at the house, who were unable to identify those who were fighting, Chelini said.

There were people from different high schools at the party, Chelini said, but he could not confirm which schools they were from or whether a rivalry factored into the brawl.

However, students and alumni from De La Salle High School in Concord and Monte Vista High School in Danville were engaged in heated conversations about the fight Sunday on Twitter. One person, whose profile picture showed him in De La Salle lacrosse gear, tweeted late Saturday night: "(My jaw is) broken in two places. Going in for surgery."

Deputies did not report any evidence that under-age drinking was taking place at the party or was a factor in the fight, Chelini said.

Contact Daniel M. Jimenez