(NEW YORK) -- Just as firefighters were getting the upper hand on multiple major wildfires burning across California, two new blazes broke out and rapidly spread overnight, dealing additional challenges to the crews battling the flames, authorities said.
In what fire officials called an unusually early start to the state's wildfire season, firefighters were scrambling to gain control of at least six massive wildland fires burning at both ends of the Golden State.
On Monday, two new wildfires erupted in Northern California, including one called the Sites Fire that ignited around 2:30 p.m. PT in Colusa County, about 60 miles north of Sacramento, according to the California Department of Forestry and Fire Protection (Cal Fire). Fueled by tall dry vegetation and fanned by wind gusts of up to 20 mph, the fire quickly spread to 10,000 acres by Tuesday morning, triggering numerous evacuations, according to Cal Fire.
The Sites Fire was 0% contained. A red flag warning signaling high fire danger was already issued for the area when the fire started, officials said.
"Hot dry conditions continue to hamper suppression efforts," Cal Fire said in an update on the Sites Fire Tuesday morning.
A cause for the fire was under investigation.
The Aero Fire in Calaveras County, in the Sierra foothills about 40 miles east of Stockton, started about 3:30 p.m. PT and spread overnight to 5,249 acres, threatening nearly 3,700 structures, according to Cal Fire. At least three structures were destroyed and another was damaged by the blaze, which was 20% contained on Tuesday morning, officials said.
The Calaveras County Sheriff's Office issued several evacuation orders for residents living in the fire zone. A shelter for people and their livestock was opened at the Calaveras County Fairgrounds Livestock Evacuation Center in nearby Angels Camp, and another shelter was opened at a veterans hall in Valley Springs, officials said.
"Firefighters had a small decrease in winds and an increase in relative humidity overnight that assisted crews with construction of fireline," Cal Fire said in a statement Tuesday. "The Aero Fire is burning in an area that has not experienced a large fire since 2003 and is burning in grass and oak woodlands."
An investigation into the cause of the blaze is underway.
The Sites and Aero fires ignited as firefighters were gaining control of the Point Fire in Sonoma County near the Wine Country towns of Healdsburg and Geyserville. As of Tuesday morning the Point Fire, which started Sunday afternoon, had burned more than 1,200 acres and was 40% contained, according to Cal Fire.
The Point Fire destroyed two structures and a firefighter was injured battling the blaze, Cal Fire said. The cause of the fire remains under investigation.
Another major Northern California fire, the Junes Fire in Butte County, was 95% contained Tuesday after burning 1,056 acres, according to Cal Fire. The blaze, which started on Saturday, destroyed one structure, Cal Fire said.
In Southern California, firefighters were making significant progress battling two major blazes in the Los Angeles area.
The largest Southern California fire, the Post Fire, erupted on Saturday afternoon near Gorman, in the Tejon Pass area about 70 miles north of downtown Los Angeles. It has burned more than 15,600 acres, prompted the evacuations of 1,200 campers at the Hungry Valley State Vehicular Recreation Area and forced the closure of Lake Pyramid, according to Cal Fire.
On Tuesday morning, the Post Fire was 24% contained, but ridge-top gusty winds of up to 55 mph were hampering efforts by firefighters to expand containment, Cal Fire said.
"Fire weather conditions are making it difficult to control the fire," Cal Fire said in a statement. "Important structures like power lines, dams, and oil pipelines are at risk. To limit the spread and to increase containment fire crews are building and reinforcing fire lines around the permitter. Aviation assets are also being used to slow down the fire and to extinguish hot spots."
Meanwhile, firefighters gained the upper hand on the Hesperia Fire, which also started on Saturday evening in San Bernardino County, triggering an evacuation warning for local residents. According to Cal Fire, the blaze, which burned 1,078 acres, was 72% contained on Tuesday morning.
Firefighters are also battling at least 11 other smaller wildfires across the state, which had all burned less than 1,000 acres, according to Cal Fire.