A massive fire erupted overnight at one of the largest and most critical refineries on the U.S. West Coast, which supplies 20% of Southern California’s motor vehicle fuels and 40% of its jet fuel.

On Thursday night, Chevron’s El Segundo refinery suffered an explosion, though official statements on what sparked the fire remain limited. Local media reported early Friday that the blaze had been contained.

Here’s why Chevron’s El Segundo refinery is so critical to the region:

Early indications from analysts familiar with the refinery suggested to Reuters that the fire would have a limited impact on the broader oil market, but could lead to a rise in jet fuel prices. 

The refinery’s total storage capacity is about 12.5 million barrels, held in a massive on-site tank farm.

As the smoke clears, the question is what disruptions will materialize - something that will likely become clearer later today.