The San Francisco Police Department have announced that they will have undercover officers in the crowd for today's NFL game between the San Francisco 49ers and the Seattle Seahawks at Candlestick Park.

Officers will wear jerseys from both teams in order to monitor the behaviour of fans during the clash between the NFC West rivals, who currently sit first and second in the division.

Police chief Greg Suhr told KTVU: "Energised fans going at each other, totally in bounds, no problem. If somebody handles somebody, it could well be a San Francisco police officer.

"You don't wanna spend the game that you spent a lot of money on a ticket in one of our padded wagons or substation or jail."

Last season, 355 fans had to be ejected from the 49ers stadium, 53 of which were for alcohol-related incidents, and 14 led to felony arrests.