The blaze broke out in an industrial area in the 6700 block of 8th Street at around 11:30 p.m. Sunday. Firefighters responded to the rear of a business and saw heavy smoke and flames from behind the building.
Officials say wood pallets and five 55-gallon drums were burning. Hazmat teams are still trying to figure out what was in the drums.
Crews knocked the fire down in about 15 minutes. No injuries were reported.
Arson investigators were working Monday to pinpoint the origin and determine the cause of the fire, Orange County Fire Authority Battalion Chief Anthony Espinosa said, adding it is possible fireworks could have been involved.
Anyone with any information on the blaze was urged to contact the Orange County Fire Authority at (714) 573-6000.
City News Service contributed to this report.