By Krystian Orlinski

WRIGHTWOOD, Calif. (Reuters) - The main highway linking Southern California to Las Vegas reopened on Thursday as authorities battled a fast-moving wildfire that raged for a third day in mountains east of Los Angeles.

More than 80,000 residents remained under evacuation orders from the so-called Blue Cut Fire, named for a narrow gorge near its origin.

It erupted on Tuesday in the Cajon Pass near Interstate 15, the primary traffic route between greater Los Angeles and Las Vegas, Nevada, to the northeast and quickly devoured canyons and hillsides filled with dense, drought-parched brush and chaparral.

As the fire's leading edge moved away from the highway on Thursday, authorities reopened Interstate 15 in both directions through the Cajon Pass, ending a two-day closure.

But the intensely burning blaze, producing cyclone-like whirls of flame, has charred some 32,000 acres near the ski resort town of Wrightwood and destroyed dozens of structures, including an unspecified number of homes, fire officials said.

Impeded by treacherous terrain, hot, dry, windy weather and the ferocious nature of the blaze itself, nearly 1,600 firefighters have so far managed to carve containment lines around just 4 percent of the fire zone, authorities said.

Much of the fire was burning across unpopulated swaths of the San Bernardino and San Gabriel mountains about 60 miles east of Los Angeles, but Wrightwood and several adjacent communities were being threatened.

An estimated 34,500 homes and nearly 83,000 people have been placed under evacuation orders, and numerous public schools have been closed as a precaution, fire officials said.

Many residents, having made it through previous wildfire emergencies unscathed, opted to stay put for the time being but packed their belongings in preparation to flee.

"I can't take the risk. Last night the smoke was blowing into town," Perry Van Dran, a Wrightwood musician and construction worker, told Reuters after filling his truck with his instruments and tools. "You could look down Highway 2 and see where the fire was burning, and that's a little too uneasy for me."

The Blue Cut fire is one of nearly 30 major blazes reported to have scorched at least 530 square miles in eight Western states this week, in the midst of a wildfire season stoked by prolonged drought and unusually hot weather, according to the National Interagency Fire Center in Boise, Idaho.

The cause of the fire was under investigation.

(Additional reporting by Alex Dobuzinskis and Nichola Groom in Los Angeles, Laila Kearney in New York and Curtis Skinner in San Francisco; Writing and additional reporting by Steve Gorman in Los Angeles; Editing by Toni Reinhold and Cynthia Osterman)