The flames burned out of control and dark smoke was visible for miles. More than 150 firefighters joined in the effort.
Part of the roof collapsed, but the other part did not. That had firefighters worried.
It started burning around 5:30 a.m. when at least 25 workers were inside the industrial complex.
"Suddenly it was a big blast," said Ignacio Guevara, who witnessed the fire. "All the doors just opened and everyone started running out."
"I just saw the people running everywhere inside the building," said Jorge Gomez, who witnessed the fire. "They were scared and didn't know what to do."
This building was home to Windsor Foods Golden Tiger Company, which processes Chinese food.
"We make egg rolls for Panda Express," said Guevera. "All sorts of fried burritos. So we have fryers, big fryers, industrial fryers, all that stuff."
Those fryers were full of more than 5,000 pounds of soybean oil.
"It takes quite a bit of heat to catch on fire," said L.A. County Fire Inspector Matt Levesque. "Under normal conditions, it's relatively safe. But in a fire, it's an accelerant. Once it gets going it can make our job a lot more challenging. And if it overflows from the vats, it can create more fire in other areas of the building."
That's exactly what happened. Only one worker sustained minor injuries. Sergio Fuentes is the victim's brother-in-law and said she hurt her arm.
"She worked in the packing," said Fuentes. "She was working right there and that's where the fire was."
Now the clean-up is on and workers are feeling fortunate.
"I know it's a big building," said Guevera. "But our lives are more important."
The owner of the building believes it is a complete loss, with an estimated damage of $5 million.