After violence marred a preseason game against the archrival Oakland Raiders, the San Francisco 49ers moved Monday to strengthen security at Candlestick Park by banning tailgating after kickoff and warning fans that rowdy behavior won't be tolerated.

In addition, 49ers CEO Jed York said he will recommend to the NFL that the annual preseason battle between the Niners and Raiders be put off next year.

"This is a game where you have a rivalry situation, and unfortunately, you have the worst segment from a very small segment of both fan bases that come and brings about this type of event," York said at the stadium.

San Francisco police, Mayor Ed Lee and 49ers officials also said officers will set up DUI checkpoints near the stadium after games and strictly forbid alcohol consumption at that time.

Earlier Monday, Lee said he was horrified as he watched violent fan confrontations at the game. Lee attended Saturday's game with Oakland Mayor Jean Quan, and both witnessed the brawling firsthand as spectators.

Two men who were initially listed as seriously injured in the violence were upgraded to fair condition, a hospital spokesperson said.