A large pungent plume released by a chemical plant triggered dispatched materials squads in the Atwater Village area in Los Angeles.
The facility, a location of Huntsman Corp., was evacuated and the city fire spokesperson reported no immediate injuries.
The spokesperson said gas expelled into the air when a small valve broke while a metal vessel was being prepared for distribution.
Reports from a helicopter said the plume dissipated to a light haze.
The substance involved was not immediately identified.
Hazardous materials firefighters used special gas meters to determine no readings of concern and most resources were being released.
Products at the Huntsman facility are used in several industries, including automotive, energy and fuels, coatings and construction and aerospace and defense.