LOS ANGELES, July 3 (Xinhua) -- A wildfire in central California rapidly expanded overnight into Thursday, forcing evacuations and a partial highway shutdown as the massive blaze grew.

According to the latest data released by the California Department of Forestry and Fire Protection (Cal Fire), the Madre Fire, ignited Wednesday afternoon in San Luis Obispo County, had spread to 52,593 acres (212.8 square km) as of Thursday evening, with only 5 percent containment.

"The fire continues to burn actively throughout the night, with greatest rates of spread observed on exposed ridge tops and drainages in alignment," the Cal Fire described the current situation, adding that the fire is the largest in California so far this year.

Evacuation orders have been issued near Highway 166 in the county and part of the highway has been closed.

The cause of the wildfire is under investigation. ■