Firefighters working in sweltering conditions and steep terrain raced to douse spot fires. [Noah Berger/AP Photo]

Los Angeles, June 18 (RHC)-- A wildfire burning northwest of the U.S. city of Los Angeles has forced the evacuation of about 1,200 people from a popular outdoor recreation area and burned more than 12,000 acres (about 4,850 hectares), authorities said.

About 400 firefighters, accompanied by 70 firetrucks and two bulldozers, are battling the blaze, authorities said. Dubbed the Post Fire, it was contained just 2 percent until Sunday evening. Los Angeles County’s first major wildfire of the year swiftly grew to nearly 23 sq miles (60sq km).

No injuries have been reported.  The cause of the inferno, which was burning about 60 miles (96 km) northwest of the Californian city, was under investigation.  The California Department of Forestry and Fire Protection said efforts to contain the fire are being hampered by high temperatures, low humidity and strong winds.

Water-dropping aircraft are working to try to halt the progress of the fire, while firefighters are constructing perimeter fire lines to get the blaze under control.  About 1,200 people were evacuated from the Hungry Valley recreation area, which has trails for motorcycles and off-road vehicles, after the fire broke out. Two structures have been destroyed so far.

Meanwhile in Northern California, a small wildfire on Sunday prompted evacuation orders and warnings for a sparsely populated area near Lake Sonoma.

Known as the Point Fire, it sent up a huge plume of dark smoke as it churned through brush and timber about 80 miles (130km) north of San Francisco, and destroyed at least one structure. It was 15 percent contained.