Nearly two dozen people under the age of 20 suffered respiratory irritations and burn injuries after exposure to "theatrical fog vapor'' at a pre-party for the Teen Choice Awards in Hollywood, a city fire official said.
Witnesses said the incident at the Avalon Hollywood resulted in chaos, calling to mind for a panicked moment Friday's shooting massacre at a movie theater in Aurora, Colo.
The incident was reported at 6:04 p.m. at 1735 N. Vine St. (map), Brian Humphrey of the Los Angeles Fire Department said.
The fog was so thick that partygoers could not see directly in front of them.
Rescuers believe a special-effect fog system -- perhaps involving carbon dioxide -- caused the injuries. Most victims felt better after fresh air and examination, Humphrey said.
"Along with respiratory irritation, a few patrons who contacted dripping liquid from apparent heavy use of smoke effect have superficial burn (injuries),'' Humphrey said.
He said that band performing at the event -- Midnight Red, a boy band -- suggested on social media that there had been a riot.
The band's Twitter account posted at 8:17 p.m.: "#Facts from tonight. Club smoke canisters malfunction. Small panic. Show cancelled by Fire team, not MNR for safety which best for all. Love."
Six people were taken to hospitals in unspecified condition. A total of 22 patients between the ages of 8 and 20 were assessed, according to Humphrey.
A hazmat team was investigating, Humphrey said.
The party was called off after the incident, he added.
Vine Street was closed between Franklin Avenue and Hollywood Boulevard while the group was assessed, he said.