CARSON, Calif. — Authorities are trying to determine what caused an explosion and fire at a large Southern California refinery.

The fire erupted late Tuesday at the Marathon Petroleum refinery in the city of Carson and firefighters brought it under control Wednesday. No injuries were reported.

Air quality officials say there's no indication any toxic gasses escaped but testing is continuing.

Marathon says its refinery is the largest on the West Coast and has a crude oil capacity of 363,000 barrels daily.

The fire caused a price spike on the gasoline trading market but an analyst says that quickly dropped and the impact on pump prices is uncertain.