The state's largest wildfire grew to nearly 300 square miles on Thursday and officials predicted the more than two-week-old blaze in south-central Montana will keep growing because of high winds and the density of dead trees.

Hazy, brown smoke hung over the area that includes the Boulder River Valley, where the movie "The Horse Whisperer" was filmed.

The fire crossed into the valley earlier this week, but so far, flames have not reached any of the historic ranches or homes there. Fire information officer Cher Fuller residents of 265 homes evacuated because of the fire would likely be allowed to return early Friday.

The blaze was sparked by lightning on Aug. 22 and has forced hundreds to evacuate. It was 45 percent contained on Thursday.

Deliberate burning as part of the firefighting strategy accounted for part of the Derby Mountain fire's increase from 185,000 acres Wednesday to about 191,000 acres on Thursday, said information officer Dixie Dies. She said wind and the density of dead trees was likely to spread the fire.

Smoke from the fire and others triggered air-quality warnings in southwestern Montana. The Department of Environmental Quality said the air in Bozeman and in the area of the fires was "very unhealthy."

In California, a pilot and firefighter were killed Wednesday when their Department of Forestry and Fire Protection plane crashed as they fought a fire in the remote Tulare County foothills, about 70 miles southeast of Fresno, authorities said.

The victims were identified as George Willett, 52, a Hanford pilot contracted to help battle the fire, and CDF Battalion Chief Robert Paul Stone, 36, of Visalia.

The crash sparked a three-acre wildfire near the other blaze.

The National Transportation Safety Board was investigating the crash.

In Nevada, crew leaders were hoping the arrival of more firefighters would help them gain ground on wildfires that have blackened nearly 375 square miles across the state's northeastern area during a four-day span.

Officials reported 32 fires touched off by lightning since Sunday, including one in Lander County that had exploded to more than 200 square miles and was only 10 percent contained.

No damage to homes or injuries were reported, but the fires continued to pose a threat to scattered ranches and mines as well as wildlife habitat, said fire information officer June McMillen.

Air quality advisories were also issued across eastern Washington state, warning residents to take precautions against heavy smoke from more than a dozen wildfires.

U.S. and Canadian fire crews were working together on two blazes, the larger of which had burned almost 255 square miles northeast of Winthrop. Nearly 1,400 firefighters were battling the blaze, which was more than 50 percent contained.