Police say Occupy San Francisco protesters attacked two officers during a march.
Police spokesman Carlos Manfredi says officers were trying to keep marchers out of an intersection when a woman came from the crowd, slashed an officer's hand with a pen knife or razor blade, then disappeared before he realized he'd been cut.
Police say a man then came out of the crowd and grabbed an officer's radio, and when the officer chased him another protester shoved the officer, leaving him with a torn uniform and a bleeding laceration on his face.
Police did not know if that protester had a weapon or if the cut came during the struggle.
Police could not find the attackers and no one was arrested.
Both officers were treated at the scene and released.