Matthew Fox has problems that extend beyond his unflattering facial hair below.

The former Lost star is under investigation for assault, as authorities tell TMZ the actor allegedly attempted to invade a party bus in Cleveland last night, only for the female driver, Heather Bormann, to block his path and for Fox to reportedly respond with a punch to her private parts and "stomach area."

Fox was handcuffed and detained. He was then released later in the night without a formal arrest being issued, although an investigation is ongoing.

Bormann spoke to TMZ this morning and explained her side of the story, saying she busted Fox's lip with a retaliatory blow in self-defense.

"He just kept staring at me with his mouth wide open and not saying anything," the driver said. "I told him, 'You have to leave buddy. You are trespassing on my bus.'"

Instead, Bormann said Fox "leaned in and started punching my crotch and breast." In turn, she took "one hand to his jaw and he was spitting blood. He stumbled backwards... this was the only way I could protect myself... from a man beating up on a woman."

Bormann is meeting with a lawyer today and will press charges. She's pictured below:

[Photos: WENN.com, Pacific Coast News]