A fast-moving brush fire near Yosemite National Park exploded in size Saturday into one of California’s largest wildfires of the year, prompting evacuation orders for thousands of people and shutting power to more than 2,000 homes and businesses.

The Oak Fire started Friday afternoon southwest of the park near the town of Midpines in Mariposa County and by Saturday had grown to nearly 19 square miles (48 square kilometers), according to the California Department of Forestry and Fire Protection, or Cal Fire.