Twenty-five people, including teenagers, received medical attention. Some suffered respiratory irritations and burn injuries after they were exposed to a special effect fogging system at a Teen Choice Awards pre-party at the Avalon nightclub at 1735 N. Vine Street.
Los Angeles Fire department spokesman Brian Humphrey said about 400 people were attending a concert for the boy band Midnight Red when the machine released a large amount of carbon dioxide.
The release of the fog created zero visibility within seconds, Humphrey said, prompting the club's staff to evacuate the building.
The band tweeted that the accident caused a "small panic" and blamed fire marshals for canceling the concert.
The Associated Press contributed to this report.