Eleven people were arrested after fights broke out between San Francisco 49ers and Las Vegas Raiders fans during Sunday’s game at Levi’s Stadium, police said.
The Santa Clara Police Department said a further 45 people were ejected from the stadium following the incidents.
Videos posted on social media appeared to show several spectators joining the clashes in the stands. Officers responded to each reported incident of fan-on-fan violence.
Police said some of the people involved in the fights who were treated as victims were unwilling to co-operate with investigations.
The rivalry between the 49ers and Raiders has continued despite the Raiders leaving Oakland several years ago.
