Hanging Lake, a treasured national landmark in Glenwood Canyon, appears to have been spared after a major blowup of the Grizzly Creek fire late Thursday, the U.S. Forest Service said.

Early Friday, firefighters had not been able to determine the extent of the damage on the ground because of flames and smoke from the fire, which has been burning out of control since Monday and has grown to 19,440 acres.

“We know the fire moved through that area,” the fire incident command team said in a statement Friday afternoon. “We are working with Forest (Service) officials to assess to what extent Hanging Lake was impacted.”

After a flyover later in the day, Scott Fitzwilliams, White River National Forest supervisor, said the flames had spared the vegetation on the lake cliffs and the wooden walkways.

“This afternoon, we flew over Hanging Lake to asses impacts from the Grizzly Creek fire,” White River National Forest posted on Twitter. “The immediate area around Hanging Lake, the boardwalk, the upper reaches of the trail did not burn.

“Other areas surrounding the lake burned intensely. Still some active fire in the area.”

Hanging Lake is one of the most popular outdoor destinations in Colorado, accessible by a steep, rocky trail about a mile from Interstate 70. Before the trail was closed by the fire, reservations were required to try to protect the lake and trail from overuse.

The Grizzly Creek fire is the top priority in the nation because it is has shut down I-70. The fire started in the median of I-70 near the Grizzly Creek recreation area about 1:30 p.m. Monday, the Glenwood Springs Post Independent reported. The cause of the fire hasn’t been determined.

Overnight Thursday, the Grizzly Creek fire, one of at least four wildfires burning on the Western Slope, grew from just over 6,000 acres to 13,441. It is zero percent contained.

Large wildfires have become more common across the West since the 1980s as the climate has changed. The higher temperatures and drier landscapes increase wildfire risk, help fires spread faster and make them harder to extinguish, according to the Center for Climate and Energy Solutions.

High heat, gusty winds and forests desiccated by severe drought have fueled the Pine Gulch fire, which has grown to 74,807 acres north of Grand Junction.

More than 700 firefighters backed by air attacks have made little headway against the fire, which has remained at 7% containment since Sunday.

The fire is the fifth largest in state history behind the High Park fire, Spring Creek fire, West Fork complex fire, and Hayman fire — the largest at 138,114 acres.

Only an abandoned structure has reportedly been burned, but some Garfield County residents have been forced to evacuate, the agency said.

Smoke from both fires settled along the Front Range creating a haze and prompting health officials to issue an advisory about poor air quality. The worst air quality was expected in the Denver metro area north to Fort Collins.

High ozone levels were also predicted to expand into Colorado Springs on Friday afternoon. The state health department advised people with heart or lung disease, older adults and young children to refrain from prolonged or heavy exercise Friday and Saturday. 

The Cameron Peak fire, which broke out Thursday about 60 miles west of Fort Collins, grew quickly from 500 acres to 5,424 acres by Saturday morning, Forest Service officials said.

The fire had closed Colorado 14 from Rustic to Gould and prompted evacuations for surrounding areas.

On Friday, another fire broke out in Grand County and had grown to 1,300 acres in the evening, the Forest Service said.

The fire was burning in the Southern Williams Fork Valley on U.S. Forest Service land and prompted mandatory evacuations about 5 p.m., the Grand County Office of Emergency Management said on Facebook.

The fire was burning in beetle-killed trees and air support has been called in, the Forest Service said on Twitter.

The Gazette’s Mary Shinn, Leslie James and Joel Millman contributed to this report