Firefighters in California say inaccessible, steep terrain and extreme fire behavior are hampering efforts to contain a massive wildfire that is threatening a famous national park.
Nearly 5,000 firefighters are battling the Rim Fire but have had to rely heavily on aircraft to slow the spread of the fire.
The U.S. Forest Service said Friday the massive blaze has swelled to more that 800 square kilometers and consumed about 82,000 hectares of land, including some of Yosemite National Park.
The fire is about one-third contained. Authorities are using an unmanned military Predator drone, similar to those used in Afghanistan, to provide information on new fires they would otherwise not be able to see.
The U.S. Forest Service said firefighters expect to fully contain the Rim Fire by Sept. 20.
The massive fire has destroyed more than 100 homes, businesses and other structures. Authorities say about 4,500 other structures are threatened by the blaze.
Mandatory evacuations are in place in at least two areas.
The cause of the fire that broke out August 17 is under investigation. It is one of dozens of large wildfires burning in the western United States, which has been plagued by a lack of snow and rainfall this year.