In pictures: Northern California firesGetty ImagesThe state's fire service has been battling 15 separate fires across nine counties including Napa, Sonoma and Yuba.Getty ImagesSome people have tried to save their homes from the flames, which have engulfed some 49,000 acres (28,000 hectares) so far.AFPNapa, Sonoma and Yuba make up California's famed wine region, lying to the north of San Francisco.AFPAt least 1,500 buildings and other property have been destroyed.ReutersAircraft have been used to drop fire retardantGetty ImagesThe California governor has declared an emergency. saying the wildfires "continue to threaten thousands of homes, necessitating the evacuation of thousands of residents".Getty ImagesThis is one of the worst fires in the state's history.Getty ImagesIt has been stoked by a combination of strong winds, low humidity and hot, dry weather.Getty ImagesIt is not yet known how the fires started.California wine country wildfires kill 13