Thursday's calm winds slowed the growth of a wildfire that has burned more than 12 square miles in the Shoshone National Forest east of Yellowstone National Park.

The Gunbarrel Fire was burning about 40 miles west of Cody and 15 to 20 miles east of the Yellowstone boundary in the North Absaroka Wilderness of the Shoshone National Forest.

Infrared mapping conducted by plane Wednesday night showed the fire covering more than 7,800 acres, the latest measurement available, fire information officer Olga Troxel said Thursday.

Fire managers are allowing the fire to burn through bug-killed timber in a remote area. A lightning strike started the fire on Saturday.

Crews have cleared brush and installed sprinkler systems around buildings along the North Fork of the Shoshone River, which at one mile away are the closest structures to the fire. Thursday's southwesterly winds pushed the fire away from the structures, Troxel said.

Meanwhile, the New Fork Lakes Fire north of Pinedale on Thursday grew from 2,500 acres to 3,000 acres, or more than 4.5 square miles. The fire was burning about 19 miles north of Pinedale in the Bridger-Teton National Forest. Investigators believe the fire was started Tuesday by an escaped campfire.

Bridger-Teton spokeswoman Mary Cernicek said the fire had not threatened any structures, but crews were clearing trees and setting up sprinklers around the Willow Creek Guard Station as a precaution. The building was about two miles from the fire, she said.

An air quality alert was issued for eastern Sublette County on Thursday morning after a good deal of smoke settled into the valley. Sublette County Health Officer Tom Johnston advised people with respiratory problems to limit their physical activities outdoors until the haze lifted.

A temperature inversion pressed the smoke down into the Upper Green River Valley in the morning, but it lifted around 12:30 p.m., an official said.

"This morning it was really shut in with smoke, but it's blown out of here pretty good," Sublette County Commissioner Joel Bousman said early Thursday evening. "It's sure better here after the wind's been blowing all afternoon."

In Yellowstone National Park, firefighters continued to battle the LeHardy Fire, which has burned about 800 acres on either side of the Yellowstone River. The fire was started Wednesday by a downed power line. A section of the Grand Loop Road north of Fishing Bridge junction remains closed because of the fire, park spokesman Al Nash said.

The fire has not threatened visitors, Nash said.

None of the fires has resulted in any injuries.

Though winds from the southwest and west are pushing the Gunbarrel Fire mostly to the north and east, the southern edge of the fire continues to creep downhill toward the North Fork corridor, said Terry Root, Wapiti district ranger for the Shoshone National Forest.

Winds gusted to more than 60 mph along ridgelines Wednesday night, Root said, pushing the fire into an extremely active phase and raising concerns among fire managers about defending lodges and cabins to the south.

Root said the fire was at times spotting, or starting in new locations from blown embers, at distances of a half-mile.

"It seemed fairly scary, and it had me pretty nervous," he said, adding that further assessments Thursday left fire managers optimistic that it would continue mostly north and east, away from structures to the south.

"Our strategy is to let Mother Nature do its thing, as long as it doesn't cause problems for people," said Todd Richardson, deputy incident commander of a team of about 100 people working on the Park County blaze.

"We're trying to lock things up as far as fuels burning down your way, and keep that highway open and safe before it becomes too late to do that," Richardson told a group of North Fork guest lodge and cabin owners Thursday.

Angie Foster, a fire management team member, said crews have installed sprinklers, hand lines and support hose around Goff Creek Lodge, located about 10 miles east of the East Entrance to Yellowstone National Park, and the property closest to the fire.

Crews are setting up similar defensive measures at Elephant Head Lodge, Absaroka Mountain Lodge and other cabins and structures to the east, depending on conditions and equipment availability, Foster said.

Foster said that the southern flank of the fire was advancing about 120 feet a day, and that a heavy helicopter expected to arrive by Friday would be able to dump water on the southern edge to slow its advance, if necessary.