EMBED >More News Videos A massive fire erupted after reports of an explosion at the Marathon oil refinery in Carson.

REFINERY FIRE | FS36 | #Carson | An explosion preceded fire in a cooling tower at the Marathon Refinery. Marathon personal keeping flames in check via fixed ground monitors while they work to depressurize the system. LACOFD assisting. — L.A. County Fire Department (@LACoFDPIO) February 26, 2020

CARSON, Calif. (KABC) -- Firefighters made progress Wednesday morning in reducing the size of a massive fire at the Marathon Petroleum refinery in Carson that sent massive flames and thick plumes of smoke into the air.The fire was visible as far away as Fullerton, with the thick black smoke rising hundreds of feet into the night sky. Some residents reported hearing a large boom in the area when the fire broke out just before 11 p.m. in the 2300 block of East 223rd Street."Like a big boom and a rumble. We do live pretty close to the train tracks, there are a couple of refineries that are very near us," resident Buster Cates said. "It's kind of hard to know what to do when you hear that. Do you stay inside, do you grab your family and run?"Both sides of the 405 Freeway and some surrounding streets were temporarily shut down in the area, but were later reopened.The refinery's own firefighters were on scene fighting the blaze and working to depressurize the system, while units from the Los Angeles County Fire Department arrived to assist.The county fire department said there was an explosion before the fire broke out in a cooling tower at the refinery.Personnel from the refinery kept the flames in check through "fixed ground monitors," the department said.Some flames were still visible by 6 a.m. Wednesday, but fire officials said that was part of a normal process called flaring operations."This is a standard engineering practice in refinery during the processing of different chemicals that are being distilled here," L.A. County Fire spokesperson Tony Imbrenda said. "There is off-gasing going on, and that gas, rather than being released into the atmosphere, is actually burned off before it gets released so that it really takes all of the dangerous constituents out of the gas before it makes its way into the environment."Imbrenda added that people in the area do not need to worry about respiratory hazards, but recommended residents stay indoors and keep windows closed.A safety officer at the refinery stated perimeter monitors did not detect harmful products in the air coming from the location due to the fire."Residual pressure from remaining flammable gas is still contributing to limited fire activity. Engineers continue work to isolate fuel sources," L.A. County Fire Department tweeted at about 2:15 a.m. Tuesday as they continued making progress on the blaze overnight.There were no reports of injuries."Everybody came out of this thing unscathed, fortunately. Very dangerous incident, we had a significant fireball when our units arrived here. So our tactics, our drilling, our preparation for these types of incident really paid dividends," Imbrenda said.The cause of the explosion remains under investigation, but officials say flammable gas came into contact with pressurized equipment. No additional information was released.The Marathon refinery is believed to be the largest on the West Coast, processing some 363,000 barrels per day.