Yosemite wildfire continues to grow as it pushes east into Sierra national forest

Giant sequoias still safe as firefighters face challenges from the warm and dry conditions fueling the blaze

The wildfire sweeping through Yosemite national park swelled to more than 4,375 acres (1,770 hectares) by Thursday morning, and is now pushing east into the Sierra national forest.

Raging across steep and rugged terrain, firefighters have faced challenges battling the blaze, which has exhibited extreme fire behavior, officials said. Warm and dry conditions as well as dried out vegetation have upped the intensity, spurring flames that, in some areas, stretched high into the canopies of the tall trees and produced large plumes of smoke that billowed into the sky.