Actor Zac Efron was reportedly hit on the mouth by a transient in a downtown area here.

The incident took place midnight Sunday.

Tmz.com reports that police officials were on patrol under the Harbor Freeway when they saw Zac and a man he identified as his bodyguard. Cops saw Zac and the other guy in a full blown melee with at least three other people.

After breaking up the fight, the officials questioned Zac. He told them they had run out of gas and were sitting in the car. Zac said while waiting for a tow truck they threw a bottle out the window -- he never said what was in the bottle -- and it smashed on the pavement near a group of transients.

Zac, who was in rehab twice last year for cocaine abuse, said the transients confronted him and the bodyguard because they believed the pair hurled the bottle at them.

According to the actor, two of the transients attacked the bodyguard and when he got out of the car to help, he got cold cocked in the mouth. Zac said: "It was the hardest I've ever been hit in my life."

The area where this occurred is rough. Cops are on high alert for drug deals and gangs. One source says Zac was "obviously intoxicated."

No one was arrested because the officials viewed it as "mutual combat."

TMZ contacted Zac's representative but so far there has been no comment.