MARIPOSA (CBS13/AP) – The latest on the fire burning in Mariposa County:

12:20 p.m.

An air quality alert has been issued for the Reno-Sparks area due to heavy smoke blowing in from a California wildfire near Yosemite National Park more than 150 miles away.

The Washoe County Health District said Wednesday the conditions are unhealthy for sensitive groups.

Officials say children, older adults and people with respiratory issues including asthma should avoid prolonged or heavy exertion outdoors.

The blaze in the rugged mountains outside of Yosemite National Park is threatening 1,500 structures and forcing thousands of nearby residents to flee their homes.

The blanket of smoke has made the downtown Reno skyline invisible from just a few miles away in neighboring Sparks.

12:05 p.m.

A wind-driven wildfire that destroyed four homes in rural northeast Nevada and damaged several more is now 90 percent contained.

Bureau of Land Management spokesman Greg Deimel (DEYE’-muhl) said Wednesday that a total of seven residences burned just east of Elko, but three of those were uninhabited.

Deimel says no one was hurt in the fire that broke out in extremely windy conditions Monday afternoon.

But five outbuildings and 16 vehicles also were destroyed by the flames that shut down part of Interstate 80 for several hours about 100 miles west of the Utah line.

Deimel says the fire charred about 11 square miles of mostly grass and sagebrush. But he says there’s virtually no fire activity within the perimeter so some of the 350 crew members on the lines may be released later Wednesday to fight other fires.

7:45 a.m.

As wildfires rage throughout the western U.S., one California blaze in the rugged mountains outside of Yosemite National Park destroyed eight structures and forced thousands of nearby residents to flee their homes.

As of Wednesday morning, the fire had scorched more than 45,000 acres, according to the Cal Fire. It is only 7 percent contained. The blaze burning since Sunday was making its way to the hills on the edge of Mariposa, a town of about 2,000 people under a mandatory evacuation order.

Record rain and snowfall in the mountains this winter was celebrated for bringing California’s five-year drought to its knees, but it has turned into a challenge for firefighters battling flames feeding on dense vegetation, officials said.

“There’s ample fuel and steep terrain,” said California Department of Forestry and Fire Protection spokeswoman DeeDee Garcia. “It makes firefighting difficult.”

The Northern California blaze is threatening at least 1,500 homes as well as powerlines that provide electricity to the park, officials said. The park remained open Tuesday but several roads frequented by tourists were closed.

The wildfire near Lake McClure, a reservoir about 50 miles (80 kilometers) east of Modesto, was 5 percent contained Tuesday evening as at least 1,400 firefighters battled it on the ground and from the air.

It’s burning near Highway 49, a historical route winding its way up California foothills of the western Sierra Nevada dotted with communities and landmarks that sprouted up during the state’s Gold Rush.

Joey Street, 49, a tree trimmer who’s lived in Mariposa for about 25 years, was among the people who were first evacuated to a Red Cross makeshift shelter set up at Mariposa Elementary School, which was later closed.

“(Firefighters) don’t have control of it now, so they’d better be safe than sorry,” Street told the Fresno Bee while waiting to be bused to an evacuation center in nearby Oakhurst.

The conditions significantly worsened from Monday to Tuesday, he said.

“Yesterday it didn’t look too bad, today you can’t even see Mt. Bullion right now, which tells me it’s getting closer,” Street said. “More ash falling from the sky tells me it’s getting closer.”

Gov. Jerry Brown on Tuesday declared an emergency, bolstering the state’s resources to battle the fire that he said has forced thousands of residents to flee and is expected to continue burning.

The cause of the blaze remained under investigation.

Smoke from the fire in Mariposa County drifted more than 150 miles away to Reno.

In a remote northeastern corner of Nevada, roughly 14 homes were damaged or destroyed by a wildfire that started Monday. Officials have lifted an evacuation advisory, allowing hundreds of people to return home and assess damage, authorities said.

Wind is driving the flames through invasive cheat grass – growing twice the norm, U.S. Bureau of Land Management spokesman Greg Deimel said.

“It is very thick, very dense,” he said. “You get the winds and the density of the grass, the fire just goes.”

Copyright 2017 The Associated Press.