A fast-growing wildfire in southern Monterey County triggered evacuation orders Wednesday as crews battled the blaze in rugged terrain near Big Sur, where firefighters are already working to contain a much larger fire. 

The Plaskett Fire was reported shortly after 11 a.m., according to the U.S. Forest Service. By early afternoon, it had grown to about 40 acres with no containment, according to Cal Fire.

The fire was burning in steep, difficult-to-access terrain. Air resources were dropping water, a helibase had been established and eight air tankers had been requested to assist firefighters with retardant drops.

Evacuation orders and warnings were issued for parts of Monterey County, including a portion of Highway 1, which officials described as facing an immediate threat to life. 

Fire tracker: Here are the latest wildfires burning across California

Firefighters were also working to protect structures along Los Perros Road, where about 30 residents live, and along Burro Road, where initial mapping indicated that five to eight structures could be threatened, Cal Fire said in a 2:10 p.m. update.

Hotshot crews were trying to reach the fire's edge while ground crews and heavy equipment worked to establish containment lines. The Cal Fire Tulare Charlie Strike Team was assisting with evacuations and preparing homes for structure defense.

The fire is burning on federal land under the jurisdiction of Los Padres National Forest. Its cause remained under investigation. Officials had not reported any injuries or confirmed damage to homes or other structures.

The new fire erupted as nearly 1,800 firefighters continued working on the Timber Fire in the Big Sur region, about 40 miles to the north.

As of Wednesday morning, the Timber Fire had burned 17,817 acres and was 23% contained, according to incident officials. The fire has threatened hundreds of structures.

Fire managers warned that hot, dry weather, low humidity and gusty afternoon winds could increase fire activity in the region.

Authorities said resources assigned to the Timber Fire were also helping respond to the new blaze, and a full wildland fire response was underway.

There's more to San Francisco with the Chronicle. Subscribe today for just 25¢.

This article originally published at New Plaskett Fire breaks out in California's Big Sur, triggering evacuation orders.