Mayor Karen Bass of the US city of Los Angeles on Saturday declared a local emergency in response to an ongoing warehouse fire that erupted Wednesday and generated heavy smoke, which has spread across the Los Angeles metropolitan area for several days.

The emergency declaration is intended to unlock additional state resources for a complex operation that city officials described as larger than a routine structure fire.

The fire broke out Wednesday afternoon at a Lineage Logistics cold-storage facility, where officials said tens of millions of pounds of frozen food are stored in a massive refrigerated building near downtown Los Angeles.

Fire officials said the building, roughly 46,000 square meters, presents unusual hazards because of its construction and contents. The fire also involved solar panels on the roof and a refrigeration system that used ammonia, prompting an early hazardous-materials response.