The Valley Fire started around 1:24 pm local time on Saturday off Highway Valley Road and Bottle Rock Road in Cobb, California.
At present, the blaze remains zero percent contained. Four fighters received second-degree burns while trying to hold back the flames. All of them were taken to the UC Davis Medical Center and are said to be in stable condition, according to Cal Fire spokesman Daniel Berlant said.
There are currently around 139 firefighters battling the blaze, with helicopters and air tankers employed, Cal Fire added.
Local authorities first issued mandatory evacuation orders for Cobb, a community with about 1,800 residents. However, these have now been expanded to include nearby Middletown, a town of around 1,300, as well as people living along State Route 29 from Clear Lake to Calistoga.
Officials had to impose several road closures as well – the largest being Highway 29 from Lower Lake to Middletown.
Local reports indicate that somewhere between 50 to 100 homes have been destroyed by the wildfire so far, and around 40 to 50 people remain trapped under various structures.
One of the latest updates reported that the flames had jumped to Highway 175 at Santa Barbara near Middletown.
Around 7 million acres across the US have burned as a result of wildfires in 2015, more than 5 million of which are in Alaska, according to the National Weather Service.
The Valley Fire is just one of 13 wildfires currently raging in California. The state’s drought conditions have left the countryside tinder dry, exacerbating the situation. Nationally, the US Forest Service has already fought more than 40,000 individual fires in 2015.