CHICAGO -- Two bare-chested fans ran out onto the field in the top of the ninth inning Thursday night and attacked Tom Gamboa, first-base coach for the Kansas City Royals.

After Michael Tucker grounded out to the pitcher for one out, two unidentified fans tackled Gamboa and began punching him. The Royals entire dugout cleared and their bullpen rushed in from the right-field bullpen, with several players jumping on the fans.

Punches were exchanged, but it wasn't clear which players threw them. Security came on the field and tried to break it up, but it was several minutes before order was restored.

The two fans were escorted off the field in handcuffs and a White Sox trainer attended to Gamboa. He had a large cut on his forehead, and was holding a towel to his face, but he walked off the field under his own power.