Southern California authorities say an explosion has occurred at an Exxon Mobil refinery in the city of Torrance, triggering a very large smokestack flare to burn off flammable product.

Torrance police Sgt. Paul Kranke says are roads are closed after the Wednesday morning incident and ash is in the air.

Fire Department spokesman Steve Deuel tells KCBS-TV that the explosion shortly before 9 a.m. happened in a processing facility and the material involved was most likely gasoline.

Deuel says a small ground fire was quickly extinguished. He says the flare system was triggered for safety reasons.

Deuel says there were two minor injuries and neither person was hospitalized.

The Police Department has told the community it's not necessary to take shelter.