Deputies responding to a report of six men fighting Sunday night found the scene clear, but were told by witnesses there had been a brief fight over a parking space.
"The altercation allegedly led to Chris Brown punching the victim," the department said in a statement released early Monday morning.
The "victim" wasn't identified, but the celebrity website TMZ, which first reported the fight outside the Westlake Recording Studio, said it also involved Frank Ocean, one of the top nominees at the Grammy Awards next month.
In a Twitter posting later, Ocean said he "got jumped by (Brown) and a couple guys" and suffered a finger cut.
It wasn't Brown's first problem in the run-up to the Grammys. His attack on singer Rihanna on the eve of the 2009 awards event overshadowed the show.
Last June, he was injured in a brawl with members of hip-hop star Drake's entourage at a New York nightclub.
No arrests were made. Brown was gone by the time deputies arrived but the department said the investigation is ongoing and Brown would be contacted later.
Email messages to Ocean's publicist and Brown's lawyer and representative were not immediately returned. A man answering the phone at the recording studio declined to comment.