Four workers suffered minor injuries after a large explosion Wednesday morning at the Exxon Mobil refinery in Torrance, according to an Exxon spokesman.
The explosion was the equivalent of a magnitude 1.7 earthquake, according to Caltech.
Residents in the area were asked by police to remain indoors after the explosion. That shelter-in-place order has been lifted, but a smoke advisory was issued by the South Coast Air Quality Management District.
About 47 firefighters responded after the explosion about 8:50 a.m. The blast was followed by a ground fire that was quickly extinguished, a Torrance fire captain said.
When firefighters arrived at the refinery, Capt. Steve Deuel said, they found flames likely fueled by gasoline.
Repairs will be needed, he added, as the explosion and fire damaged a portion of the refinery. But the facility was operational during the incident, and it continues to run.
"We can't just shut a refinery down," he said, saying that would be a lengthy process.
But Cal/OSHA is investigating the incident and has ordered all operations shut down at the unit where the explosion occurred until it can be safely operated, said Cal/OSHA spokeswoman Erika Monterroza.
Exxon Mobil spokesman Todd Spitler said when the incident occurred refinery workers activated emergency procedures.
"Our top priority is the safety and health of our employees and neighbors," he said. "We regret this incident and will work with appropriate authorities to conduct a thorough investigation of the cause. We apologize for any inconvenience that this incident may have caused nearby residents."
Just after 11 a.m., Torrance police and Exxon Mobil officials said all employees were accounted for.
Spliter said four contractors were taken to Long Beach Memorial Medical Center for treatment of minor injuries. Three have since been released, and one remains under evaluation.
"The refinery's flare system is operating as designed and will continue to safely burn hydrocarbon gases while we stabilize refinery operations," he said. "The non-impacted units of the refinery continue to operate."
No harmful emissions were detected, Spitler said. But the AQMD, which was at the refinery assessing air quality, issued the smoke advisory. A hazardous materials team was also at the scene.
Meanwhile, a claims hotline -- (844) 631-2539 -- has been established for residents who might have been impacted by the incident.
Congressman Ted Leiu (D-Torrance) weighed in on the explosion in a statement Wednesday afternoon. He said he is in touch with the agencies investigating the incident.
"First and foremost, I am thankful the injuries sustained in the explosion were minor. I hope for the speedy recovery of all those effected," he said. "My office stands ready to provide any assistance as needed. I also note this is the third explosion at this refinery since 1988. I hope the resulting investigation will help prevent future explosions at this refinery."
Residents took to Twitter on Wednesday morning, reporting that there had been an explosion and that ash was falling from the sky.
Caltech seismologist Egill Hauksson said the Torrance explosion registered on a nearby seismometer operated by the Caltech/USGS Southern California Seismic Network. The shaking was equivalent to a magnitude 1.7 quake and was only felt in the immediate vicinity of the explosion.
The blast at the Exxon Mobil refinery in Torrance is one of string of blasts over several decades at oil refineries along the South Bay.
Some blasts at the Torrance oil refinery have been deadly.
In 1988, one person was killed and nine others injured – some suffered serious burns -- in a massive blast that resulted in a criminal investigation. At the
Years later in 1994, 28 people were injured after unstable gases leaked from a disconnected pipe that caused an explosion with flames shooting 40 feet into the air.
Gilbert Griego, 70, said he was watching television at home with his daughter-in-law and grandson when the house shook. He has lived near the refinery for about 65 years.
"My daughter-in-law thought it was an earthquake," he said. "I didn't think it was because I didn't feel the ground move."
Looking at the flames from his home, which sits near the intersection of Crenshaw and Del Amo boulevards, he said this incident wasn't too bad.
He recalled an 1979 oil tank fire at the Mobil Oil facility that sits behind his house. He said that disaster forced the evacuation of their neighborhood.
Deuel said early Wednesday that the incident could be a result of a petroleum product leak.
A white foam insulation product was sent into the sky and landed in nearby streets, he said. He urged residents to call a 24-hour hotline, at (310) 505-3158, if they have any concerns about the product.
Students and staff at 14 schools in the area, including seven elementary schools, were sheltering in place, said Tammy Khan, a district spokeswoman. Outdoor activities were limited for students in schools close to the refinery on the north and west sides of the district.
The refinery is at 3700 W. 190th St. in Torrance. It covers 750 acres and employs about 650 employees and 550 contractors. The refinery processes an average of 155,000 barrels of crude oil per day and produces 1.8 billion gallons of gasoline a year.
State Assemblyman David Hadley (R-Manhattan Beach), whose district includes the South Bay, said on Facebook that his office had contacted Exxon Mobil and emergency services "to learn what we can and to be of service as needed in the South Bay."
"Please keep the employees and neighbors of the facility in your thoughts and prayers," Hadley said.