The Detwiler Fire, which is menacing the former gold rush town of Mariposa in the Sierra Nevada foothills, is only 10 percent contained, the California Department of Forestry and Fire Protection, or Cal Fire, said on its website.
“We’re doing everything we can to protect that town and all the other communities in that area,” Amy Head, a spokesman for Cal Fire, said.
Mariposa is 50 miles outside Yosemite National Park and largely dependent on tourism.
Governor Jerry Brown declared a state of emergency for Mariposa County on Tuesday.
More than 3,000 firemen, working in temperatures of 90 to 96 Fahrenheit (32 to 36 Celsius), were battling the fire, which has charred 70,596 acres, Cal Fire said.
It has expanded by more than 22,000 acres since yesterday morning. Cal Fire said it has burned 45 buildings and damaged another six since it began on Monday. The cause of the fire is under investigation.
The fire came within a half-mile of Mariposa on Wednesday, said Cal Fire spokeswoman Shanelle Saunders. The town’s 2,000 residents were ordered on Tuesday to evacuate.
Yosemite National Park remained open. Saunders said the biggest concern with the park on Thursday was air quality due to heavy smoke.
The community of Coulterville was evacuated on Wednesday, Saunders said.
The Detwiler Fire, named after a road near where it started, was threatening 1,500 structures, Cal Fire said.
Meanwhile, in Montana, officials said that a 19-year-old firefighter was killed on Wednesday when part of a tree fell on him while he was combating the so-called Florence Fire north of Seeley Lake.
A total of 44 large fires across 11 western states were burning on Thursday, according to the National Interagency Fire Centre’s website.
As firefighters handled those blazes, the National Science Foundation announced that a study it had underwritten had found wildfires create their own weather, such as updrafts and eddies, which cause flames to spread out of control.
The findings from researchers at San Jose State University, who took measurements near a 2014 wildfire, confirm previous discoveries which were done through computer simulations, instead of in the field, the foundation said in a statement.