The fire in central Colorado had burned only about 100 acres but was dangerously close to two densely populated housing developments near the town of Silverthorne, about 60 miles (97 kilometers) west of Denver.
"This area, there is a lot of homes that are pretty tightly packed together," U.S. Forest Service spokesman Adam Bianchi said. "Being a resort town, there's a need for a lot of housing and there's only so much available space for good land to build on."
Bianchi said the Buffalo Fire had come to within about 200 yards (183 meters) of a subdivision that includes condos, apartments and pricey homes. The closest ski resort to the fire, Keystone, is about 8 miles (12.8 kilometers) away and across a large reservoir.
About 50 firefighters were battling the blaze initially, but more were on the way, along with heavy air tankers and helicopters.
"I was absolutely shocked by how fast it spread," Silverthorne resident Jake Schulman told The Summit Daily after spotting the fire while hiking.
"There were big black rolling clouds coming off it and it had gotten to the edge of the forest, right next to the neighborhood," he added.
The fire had not destroyed any homes as of Tuesday night.
Colorado's largest blaze also kept burning in the San Juan National Forest, which has been closed to the public to try to prevent additional fires. The 416 Fire north of Durango in southwest Colorado has burned about 36 square miles (about 93 square kilometers) and is partially contained. No homes have been lost.
It's burning in the Four Corners region where Colorado, New Mexico, Arizona and Utah meet that is at the center of a large patch of exceptional drought. Much of the U.S. West is experiencing some level of drought.
More than 900 firefighters were dealing with rough and inaccessible terrain, and residents of more than 2,000 homes have been forced to evacuate since the flames ignited June 1.
Meanwhile, additional firefighters were headed to Wyoming to work on a wildfire that has exploded in size and prompted evacuations near the Colorado border.
The Badger Creek Fire grew rapidly Monday because of strong winds and dry conditions and had scorched about 3.6 square miles (9.3 square kilometers) of mostly beetle-killed forest. Several small communities of permanent and seasonal residences were ordered evacuated, but no buildings were burned.
Large wildfires also forced evacuations farther west.
In central Utah, a wildfire fed by dry conditions and swift winds consumed more than 10 square miles (26 square kilometers) and burned a cabin. The Trail Mountain Fire began as a prescribed burn but grew out of control last week.
A wildfire burning grass and brush in central Washington threatened several dozen homes and other infrastructure, while more than 250 firefighters raced to the hills overlooking Los Angeles to battle a blaze in thick brush surrounded by large homes.
The latest fires are stoking fears that a dry winter will lead to a dangerous fire season this summer in the West.
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