LOS ANGELES (Reuters) - The unexplained release of a large vapor cloud on Friday from an Exxon Mobil Corp refinery near Los Angeles prompted authorities to sound public safety sirens, but no toxic fumes were detected and no one was hurt, a fire official said.
The mishap was reported around sunset in Torrance, California, at a refinery that had been largely shut down since an explosion and fire at a processing unit on Feb. 18 injured four workers and destroyed emissions-controlling equipment.
That blast led state regulators to cite the company for 19 occupational safety violations at the 149,500-barrel-per-day refinery, with $566,600 in penalties.
A plan to restart the refinery last month was indefinitely postponed after a Sept. 6 leak of highly toxic hydroflouric acid.
As a precaution on Friday, city officials sounded sirens warning area residents to remain indoors with windows and doors closed, and traffic barriers were lowered over a street that runs along the refinery's eastern edge, Torrance Fire Department Captain Bob Millea said.
But all-clear chimes were sounded within a half-hour of the first alarm from the incident, Millea told Reuters.
He said the vapor appeared to be a large steam cloud that rose 150 to 200 feet in the air and drifted eastward from the refinery before dissipating.
According to Millea, there were no reports of unusual odors, and air-quality sampling afterward found no toxic chemicals present outside the plant.
No one was reported to have been injured or sickened, or to have sought medical treatment, he added.
While the vapor came from inside the plant, its precise origin and cause was under investigation, Millea said.
Company spokesman Todd Spitler said an "upset" in a refinery unit triggered the release, which was "primarily composed of steam" and there was no danger to public health. The Los Angeles City News Service reported the vapor escaped from a leak in an 8-inch line.
The company announced last month that it had reached an agreement to sell the Torrance plant and associated facilities, which employ some 1,400 staff and contractors, to New Jersey-based PBF Energy for $537.5 million plus working capital.
The refinery is expected to be back to full production by the time the transaction closes in 2016.
The refinery had furnished about 10 percent of California's gasoline supply and its outage helped push Los Angeles-area pump prices to over $4 a gallon in July.
(This story has been refiled to fix typo in paragraph 2)
Additional reporting by Erwin Seba in Houston; editing by Jason Neely