Blazes form California's largest wildfire in history

A firefighter knocks down hotspots to slow the spread of the River Fire (Mendocino Complex) in Lakeport, California, U.S. July 31, 2018. (REUTERS/Fred Greaves/File Photo)

Two blazes mercilessly charring northern California have grown so rapidly that they became the US state's largest in recorded history, authorities said.

Collectively dubbed the Mendocino Complex, the wildfires have burned through 283,800 acres (114,850 hectares) -- an area nearly the size of the sprawling city of Los Angeles -- and are just 30 percent contained, according to state fire authority CalFire.