July 20 (UPI) -- More than 3,000 firefighters are now battling the Detwiler Fire near California's Yosemite National Park -- which has grown to more than 70,000 acres, officials said Thursday.
Cal Fire said nearly 71,000 acres have burned so far and that the blaze, which started Sunday and is spreading quickly, remains only 10 percent contained.
Forty-five structures have been destroyed and six damaged, with hundreds more threatened. The fire is also endangering power lines leading to Yosemite National Park, officials added.
"Firefighters faced high temperatures along with dry and drought stressed chaparral and grass. Steep and inaccessible terrain continues to challenge control lines," a Cal Fire statement said. "The fire encroaches on culturally and historically sensitive areas."
Firefighters are dealing with flames up to four feet, with some flares about 25 feet, Jeff Marshall, a fire behavior analyst told the Los Angeles Times.
Officials said smoke from the wildfire can be observed as far away as Idaho, and is affecting visibility and health in California's Sierra Nevada, Yosemite and foothill communities.
Cal Fire said 3,175 fire fighters, 413 fire engines, 9 air tankers and 14 helicopters are trying to extinguish the fire -- which is currently among 37 active large fires in a dozen western U.S. states.
Earlier Wednesday, the town of Mariposa was evacuated -- an order that extended to the towns of Coulterville and Greeley Hill by the end of the day. At least 5,000 people have been ordered out of the area so far.