A fast-moving wildfire in central California’s San Luis Obispo County has forced evacuations and partially shut down Highway 166, according to Xinhua.

Known as the Madre Fire, it broke out Wednesday afternoon and has since scorched over 52,000 acres, with containment at just 5 percent, according to Cal Fire.

Officials say the fire is spreading rapidly, especially across ridge tops and drainages, and remains highly active overnight. It is now the state’s largest wildfire of the year.

The cause of the blaze is still under investigation, Xinhua reported.