Fox, most popular for his television roles in Lost and Party of Five, apparently tried to board a party bus -- full of people who didn't know him -- early Monday morning, when the vehicle's female driver stopped him.
The 45-year-old actor allegedly punched the driver in her chest and stomach area, after which the woman punched Fox back, cutting his lip, according to a police report obtained by The Hollywood Reporter.
While Fox was handcuffed by an off-duty police officer, the actor was not arrested. He was briefly detained and released by authorities on Monday.
The woman, identified by TMZ as Heather Bormann, claims the actor appeared to be drunk.
He just kept on staring at me with his mouth wide open and not saying anything. I told him, 'You have to leave buddy. You are trespassing on my bus, Bormann, 29, told TMZ.
I took one hand to his jaw and he was spitting blood. He stumbled backwards . . . this was my self-defense, she added.
No word on whether or not Bormann intends to press charges.
Fox has been noticeably absent from Hollywood since wrapping up six seasons of Lost in 2010. He is set to return from his acting hiatus in 2012, including a small role in the post-apocalyptic thriller, World War Z with Brad Pitt.