(CNN) -- Firefighters in northern Arizona are racing to strengthen their fire lines in the rugged, mountainous terrain near Flagstaff, as they wait for a raging wildfire to be fanned as winds pick up Friday.
"Tomorrow is where the real concern is. We do expect it to pick up. It's a red flag day," said Gerry Blair, a spokesman for the region's interagency emergency center.
"Some pretty significant burnout operations are taking place today," he said.
More than 900 firefighters from several Western states have been working on slopes up to 10,000 feet high since Sunday. Those slopes can funnel the winds, making things worse.
Crews are working on fire lines north, south and west of the flames, which have scorched more than 14,500 acres.
The blaze, called the Schultz fire for a pass that fans the winds, is 25 percent contained. Authorities expect to fight it for some time.
Winds were expected to reach 14 miles per hour Thursday, then calm overnight before picking up Friday, with temperatures in the high 90s, according to CNN meteorologist Chad Myers.
The flames have threatened homes, critical watersheds and wilderness administered by the Coconino National Forest. Hundreds of people were evacuated from the fire's east flank after the blaze started, but many residents were allowed to return Wednesday. A pet shelter where many people left their animals announced they could start picking them up today.
Lucy Sullivan considers herself lucky. She returned to find that her house reeked of smoke, but otherwise was undamaged. She can live with the smell. "You bet. To be home is fantastic," she said.
In some cases, the fire came within 100 feet of homes but was stopped by fire lines, Blair said.
Authorities hope more evacuations won't be necessary, but aren't ruling them out. "Remember, it's a wildfire. Anything can happen," said Deputy Incident Commander Tony Sciacca.
To date, almost $3 million has been spent on the effort to contain the blaze. Four air tankers and seven helicopters are being used to fight the fire, as well as 56 engines and 11 water tankers. So far, no firefighters have been seriously injured, according to Sciacca.
The fire started Sunday from an abandoned campfire, and the Forest Service is offering a $2,500 reward for information about who may be responsible.
U.S. Highway 89, closed earlier in the week because of the smoke, is open. But authorities warn it could be closed again if conditions worsen.
CNN's Moni Basu contributed to this report.